(,  MECHANICAL  DRAWING 

FOR 

I  HIGH  SCHOOLS, 

A  TEXT  WITH 
PROBLEM  LAYOUTS 


BY 
THOMAS  E.  FRENCH  AND  CARL  L.  SVENSEN 

DEPARTMENT  OF   ENGINEERING   DRAWING,   THE   OHIO   STATE   UNIVERSITY 

MEMBERS  AMERICAN   SOCIETY   OF   MECHANICAL   ENGINEERS,   SOCIETY 

FOR  THE   PROMOTION   OF  ENGINEERING   EDUCATION,   ETC. 


FIRST  EDITION 

' 


McGRAW-HILL  BOOK  COMPANY,  INC, 
239  WEST  39TH  STREET.    NEW  YORK 


LONDON:  HILL  PUBLISHING  CO.,  LTD. 
6  &  8  BOUVERIE  ST.,  E.  C. 

1919 


COPYRIGHT,  1919,  BY  THE 
MCGRAW-HILL  BOOK  COMPANY,  INC. 


THE     MAPLE     PRESS     YORK    PA 


PREFACE 

Industrial  educators  are  generally  agreed  that  a  textbook  is 
necessary  for  the  most  sucessful  teaching  of  mechanical  drawing. 
However,  several  important  considerations  are  involved  in  the 
selection  of  a  suitable  text.  It  "should  be  more  than  a  collection 
of  problems.  It  should  present  the  subject  in  a  clear,  orderly 
and  logical  arrangement  of  the  divisions,  explaining  why  each 
rule  or  custom  is  made,  and  illustrating  with  examples  represent- 
'  ing  good  modern  practice." 

A  survey  of  mechanical  drawing  in  high  schools*  recently  made 
by  the  authors  showed  that  "a  system  of  standardization  appears 
to  be  needed  to  give  the  subject  the  standing  to  which  it  is  en- 
titled as  a  cultural  subject  as  well  as  a  practical  one,  a  real  lan- 
guage to  be  studied  and  taught  in  the  same  way  as  any  other 
language." 

The  purpose  of  this  book  is  to  present  mechanical  drawing  as  a 
definite  educational  subject  with  the  following  objectives: 

To  develop  the  power  of  visualization; 

To  strengthen  the  constructive  imagination; 

To  train  in  exactness  of  thought; 

To  teach  how  to  read  and  write  the  language  of  the  industries; 

To  give  modern  commercial  practice  in  making  working  draw- 
ings. 

The  standardizing  of  mechanical  drawing  by  the  logical  ar- 
rangement of  its  subject  matter  into  grand  divisions  will,  it  is 
believed,  make  both  teaching  and  learning  easier. 

The  first  seven  chapters  comprise  a  complete  textbook  which 
may  be  used  with  any  problems.  The  paragraphs  are  numbered 
for  easy  reference.  The  eighth  chapter  is  a  complete  problem 
book,  in  which  the  number  of  problems  in  each  division  is  such 
that  a  selection  may  be  made  for  students  of  varying  ability, 
and  that  a  variation  from  year  to  year  may  be  had.  The  prob- 
lems have  references  to  articles  in  the  text,  and  the  order  may  be 

*  Bulletin  issued  by  Dept.  of  Public  Instruction,  State  of  Ohio. 


vi  PREFACE 

varied  to  suit  the  particular  needs  of  a  school.  Definite  speci- 
fications and  layouts  are  given  for  most  of  the  problems,  thus 
making  it  possible  for  the  instructor  to  use  his  time  efficiently  in 
teaching  rather  than  in  the  drudgery  of  detail,  while  the  time 
ordinarily  wasted  by  the  pupil  in  getting  started  can  be  used  in 
actual  drawing. 

More  than  enough  is  included  for  two  years'  work  in  the  aver- 
age high  school.  The  authors  will  at  any  time  be  pleased  to 
advise  in  the  selection  of  problems  or  arrangement  of  courses. 

COLUMBUS,  OHIO. 
July  18,  1919. 


CONTENTS 

PAGE 
PREFACE v 

CHAPTER  I — THE  LANGUAGE  OF  DRAWING 1 


CHAPTER  II — LEARNING  TO  DRAW 3 

Attaching  the  paper — Sharpening  the  pencil — Ruling  lines — 
Positions  for  triangles  —  Parallel  lines  —  Perpendicular  lines  — 
Drawing  arcs — Using  the  compasses — Using  the  bow  pencil — 
Using  the  curve — Measuring — Scales — Drawing  to  scale — Spacing 
— Using  the  dividers — Lettering — Single  stroke  vertical  capitals — 
Vertical  lower  case — Inclined  capitals — Inclined  lower  case — 
Composition. 

CHAPTER  III — THEORY  OF  SHAPE  DESCRIPTION 21 

Describing  objects  by  views — Positions  of  views  in  working 
drawings  —  The  relation  of  views  —  Orj^^rapjijc^projectioii  — 
Principles  of  projection — Objects  with  parallel  surfaces — Objects 
with  inclined  surfaces — Objects  with  curved  surfaces — Freehand 
sketching  studies — Sections  —  Auxiliary  views  —  Revolution  — 
Revolution  chart — Pictorial  drawing — Isometric  drawing — Non- 
isometric  lines — Angles — Circles — Sections — Making  an  isometric 
drawing — Oblique  drawing — Making  an  oblique  drawing — Cabinet 
drawing — Perspective  drawing — Making  a  perspective  sketch. 

CHAPTER  IV — PRINCIPLES  OF  SIZE  DESCRIPTION 51 

Lines,  figures,  arrows,  etc., — Placing  dimensions — Theory  of 
dimensioning — Rules  for  dimensioning — Use  of  decimals — Dimen- 
sioning assembled  parts — Sketching  and  measuring — Notes  and 
specifications — Checking  a  drawing. 

CHAPTER  V — TECHNIC  OF  THE  FINISHED  DRAWING 64 

Alphabet  of  lines — Order  of  penciling — Inking  and  tracing — To 
make  a  tracing — Order  of  inking — Erasing — Titles — Bill  of  mate- 
rial— Screw  threads — The  helix — Bolts  and  other  fastenings — 
U.  S.  Standard  bolts— To  draw  a  bolt— S.  A.  E.  standard  bolts- 
Cap  screws — Machine  screws — Set  screws — Wood  screws — Con- 
ventional symbols — Blueprinting — To  make  a  blueprint. 

CHAPTER  VI — DRAFTING,  MECHANICAL  AND  ARCHITECTURAL  ....     84 

.     Working  drawings — Detail  drawings — Assembly  drawings,  Shade 

lines — Choice  of  views — Choice  of  scale — Grouping  and  placing 

parts — Conventional     representation — Sections     through     ribs — 

Rule  of  Contour — Gears — Cams — Architectural  drawing — Prelimi- 


viii  CONTENTS 

PAGE 

nary  sketches — Display  drawings — Working    drawings — Plans — 
Elevations  and  sections — Details — Symbols,  etc. 

CHAPTER  VII — GRAPHIC  SOLUTIONS  AND  SHEET  METAL  DRAFTING  .  105 
Geometrical  drawing,  Lines — Angles — Triangles — The  hexagon — 
The  octagon — Arcs  and  tangents — The  ellipse — Approximate  ellip- 
ses— Sheet  metal  drafting — Development — Prisms  and  cylinders — 
Pyramids  and  cones — True  length  of  a  line — Transition  pieces, 
development  by  triangulation — Intersections — Intersecting  prisms 
— Intersecting  cylinders — Cylinders  and  prisms — Cylinders  and 
cones — Planes  and  curved  surfaces — Seams  and  lap — Practical 
problems. 

CHAPTER  VIII— PROBLEMS 134 

INDEX  .    219 


MECHANICAL  DRAWING 
FOR  HIGH  SCHOOLS 


CHAPTER  I 
THE  LANGUAGE  OF  DRAWING 

1.  Language  is  defined  as  the  expression  of  thought.  Every 
educated  person  wishes  to  be  able  to  express  himself  readily  and 
easily,  to  convey  his  thoughts  so  accurately  that  they  cannot  be 
misunderstood;  and  to  be  able  to  understand  the  exact  meaning 
expressed  by  another  person.  For  this  reason  we  make  an  ex- 
tended study  of  English,  until  we  know  its  grammar  and  idioms 
and  style.  We  read  literature  and  practice  composition  in  order 
to  become  thoroughly  familiar  with  the  language. 


FIG.   1. — A  perspective  drawing. 

2.  But  if  we  attempt  to  describe  in  words  the  appearance  and 
details  of  a  machine,  or  bridge,  or  building,  we  find  it  not  only 
difficult  but  in  most  cases  impossible.  Here  we  must  use  another 
language,  the  universal  graphic  language  of  drawing.  Thus  when 
words  fail  to  give  a  complete  or  accurate  description  we  find  books, 

1 


2    .   »!*r^    i         *  fefaH4NlCAL  DRAWING 

magazines  and  nWsp&pefs"  using  pictures,  diagrams  and  draw- 
ings of  various  kinds.  For  illustrative  purposes  perspective 
drawings,  Fig.  1,  which  show  the  object  as  it  actually  appears  to 
the  eye  are  often  used.  A  written  description  of  a  new  piece  of 
furniture  would  have  to  be  very  long  to  tell  all  about  it,  and  even 
then  might  be  misunderstood.  A  picture  would  serve  the  purpose 
much  better,  but  the  picture  would  not  show  the  exact  method 
of  construction  and  would  give  only  the  external  appearance 
without  telling  what  was  inside.  It  would  be  impossible  to 
construct  a  locomotive  or  an  airplane  either  from  a  word  de- 
scription or  a  picture.  The  pictorial  methods  of  drawing  are  thus 
not  suitable  for  constructive  work. 

3.  Fortunately  another  form  of  description  has  been  developed 
by  which  the  exact  shape  of  every  detail  may  be  defined  accu- 
rately and  quickly.  It  consists  of  different  views  of  an  object 
arranged  according  to  a  definite  system,  with  lines  and  figures 
added  to  tell  the  sizes.  This  is  called  mechanical  drawing,  and 
it  forms  so  important  a  part  of  all  industrial  and  mechanical 
work  that  it  is  called  the  " language  of  industry." 

The  language  of  drawing  has  its  own  orthography  and  grammar 
and  style,  its  idioms  and  abbreviations,  and  its  study  not  only 
gives  one  the  ability  to  express  thoughts  hitherto  impossible 
but  develops  the  constructive  imagination  and  the  habit  of  exact 
thinking. 


CHAPTER  II 
LEARNING  TO  DRAW 

4.  The  previous  chapter  explained  the  necessity  for  drawing  in 
all  industrial  work,  and  that  it  was  really  a  new  language.  Some- 
times drawings  are  made  freehand,  but  for  accurate  work  it  is 
necessary  to  use  instruments.  In  learning  to  read  and  write  in 
this  language  we  must  first  learn  what  tools  and  instruments  to 
use,  and  how  to  use  them  accurately,  skilfully  and  quickly. 


FIG.  2. — Adjusting  the  paper. 

5.  Attaching  the  Paper. — Mechanical  drawings  are  usually 
penciled  on  fairly  heavy  unruled  paper,  either  cream  color  or 
white,  which  is  held  in  place  on  a  soft  pine  drawing  board  by 
thumb  tacks.  The  drawing  board  must  have  its  left  hand  and 
lower  edges  very  straight  and  accurately  square  with  each  other, 
as  these  are  the  "working  edges." 

3 


4  MECHANICAL  DRAWING 

In  fastening  the  paper  lay  it  on  the  board  with  its  left  edge  an 
inch  or  so  from  the  left  edge  of  the  board,  place  the  T-square  in 
the  position  of  Fig.  2,  and  "true  up"  the  paper  with  the  T-square 
blade.  Holding  the  paper  in  position,  move  the  T-square  down 
as  in  Fig.  3  and  put  a  thumb  tack  through  each  of  the  corners, 
pushing  them  in  until  the  heads  clamp  the  paper.  For  sheets  of 
firm  drawing  paper  not  larger  than  12"  X  IS"  the  two  lower  tacks 
may  be  omitted. 


FIG.  3. — Fastening  the  paper. 


6.  Sharpening  the  Pencil. — A  draftsman  uses  a  hard  pencil 
with  a  long  sharp  point  so  that  his  work  may  be  very  accurate. 
Drawing  pencils  are  graded  by  letters,  from  65  (very  soft  and 
black),  55,  45,  35,  25,  5,  HB,  F,  H,  2H,  3H,  4#,  5H,  6H,7H, 
8H,  $H  (extremely  hard).  4#  and  6H  are  the  usual  grades  of 
hard  pencil  used  for  drawing  lines,  while  H  and  2H  are  used  for 
sketching  and  lettering.  The  ordinary  No.  2  writing  pencil  is 
about  the  same  grade  as  HB  or  F. 

Sharpen  the  pencil  by  cutting  away  the  wood  at  a  long  slope 
as  shown  in  Fig.  4, A,  being  careful  not  to  cut  the  lead,  but  ex- 
posing it  about  a  quarter  of  an  inch.  Then  shape  the  lead  to  a 
long  conical  point  by  rubbing  it  back  and  forth  on  a  sandpaper 


LEARNING  TO  DRAW  5 

pad  or  fine  file,  rotating  it  slowly  in  the  fingers.  Have  this  sharp- 
ener at  hand  and  keep  the  lead  sharp  by  frequent  rubbing. 

Never  sharpen  a  pencil  over  the  paper  or  drawing  board. 

Pencil  lines  must  be  fine,  light,  clear  lines.  Get  the  habit 
when  drawing  long  lines  of  rotating  the  pencil  so  as  to  keep  a 
sharp  cone  on  the  point. 


FIG.  4. — Sharpening  the   pencil. 

.  The  foundation  of  mechanical  drawing  is  the  line,  so  a  set  of 
the  different  kinds  of  lines  used  is  called  the  alphabet  of  lines. 
These  are  explained  in  Art.  62. 


FIG.  5. — Drawing  a  horizontal  line. 

7.  Ruling  Lines. — All  the  lines  in  a  mechanical  drawing  are 
made  with  the  aid  of  some  instrument  as  a  guide  for  the  pencil 
or  pen.  Horizontal  lines  are  always  drawn  with  the  upper  edge 
of  the  T-square  blade  as  a  guide.  Hold  the  head  of  the  T-square 
against  the  left  edge  of  the  board  with  the  left  hand,1  and  always 
move  the  pencil  from  left  to  right,  Fig.  5. 

1  Left-handed  persons  reverse  this  rule,  using  the  T-square  on  the  right 
edge. 


6 


MECHANICAL  DRAWING 


The  pencil  should  be  held  about  an  inch  from  the  point  and 
inclined  slightly  in  the  direction  in  which  the  line  is  being  drawn. 


FIG.  6. — Drawing  a  vertical  line. 


4-5 


•-75  ' 


90 


o 


FIG.  7. — The  45  degree  and  30-60  degree  triangles. 

Vertical  lines  are  drawn  by  using  a  triangle  held  against  the 
T-square.  Always  have  the  vertical  edge  of  the  triangle  toward 
the  left  and  draw  up  from  the  bottom  to  the  top,  Fig.  6. 


LEARNING  TO  DRAW 


Horizontal 


f 5  degrees  with  hor. 
75  //       ^"        "   verf: 


3O  degrees  w/fh  hor. 
'  6O  u      u      "     verf: 


4-5  degrees  with  hor. 


verf:      i  3O   " 


6O  degrees  with  hor. 


"  verf.'     ~  /5 


75  degrees  w'fh  hor. 


«    verf- 


Vertical 


Verticaf 


U 


75  degrees  with  hor. 
15    *       *         »   verf: 


6O  degrees  w/'fh  hor. 


4-5  degrees  wifh  hot: 


3O  degrees  wirh  hor. 


vert.       '    4-S    u       »         "    verf:       «  6O  - »         * 


verf: 


15 degrees  w/fh  hor. 
75   "       "         "    verr. 


rfor/zonfaf  A/I   Together 

FIG.  8. — Positions  of  the  triangles. 


8 


MECHANICAL  DRAWING 


The  45°  triangle,  has  two  angles  of  45°  and  one  of  90°.  The 
30°-60°  triangle  has  angles  of  30°,  60°  and  90°,  Fig.  7. 

Inclined  lines  at  30°,  45°  and  60°  are  drawn  with  a  single 

triangle  held  against  the  T-square. 
Other  angles,  varying  by  15°  may 
be  drawn  by  using  the  two  tri- 
angles in  combination  with  the 
T-square.  The  methods  of  obtain- 
ing the  different  angles  are  shown 
in  Fig.  8. 

8.  Parallel     lines — other     than 
horizontal,   are   drawn  by  using  a 
triangle    in    combination    with    a 
T-square    (or    other   triangle),    as 
shown  in  the  "  movie"  Fig.  9.     To 
draw  a  line  parallel  to  the  given 
line  (1),  place  a  triangle  against  the 
T-square  (2),  and  move  them  to- 
gether until  the  hypotenuse  of  the 
triangle  matches  the  line  (3) .    Hold 
the  T-square  firmly  and  slide  the 
triangle    in    the    direction    of    the 
arrow  until  the  desired  position  of 
the  parallel  line  is  reached  (4). 

9.  Lines  perpendicular  to  each 
other  may  be  drawn  by  using  a 
triangle  in   combination  with  the 
T-square    or    another   triangle   as 
shown  in  the  "movie"  of  Fig.  10. 
To  draw  a  line  perpendicular  to  a 
given  line   (1).     Place   a  triangle 
against  the  T-square  (2),  and  move 
them  together  until  the  hypotenuse 
of  the  triangle  matches  the  line,  as 
at  (3).      Turn  the  triangle  about 
its  right-angled  corner  as  indicated 

at  (4),  until  it  is  in  the  position  shown  at  (5)   when  the  per- 
pendicular line  can  be  drawn  on  the  hypotenuse  of  the  triangle. 
10.  Drawing  Arcs. — Drawings  are  made  up  of  straight  lines 
and  curved  lines,  the  curved  lines  generally  being  circles  or  parts 
of  circles,     Circles  larger  than  one  and  one-half  or  two  inches 


FIG.  9. — Drawing  a  parallel  line. 


LEARNING  TO  DRAW 


FIG.  11. 


FIG.  10. — Drawing  a  perpendicular 
line- 


in  diameter  are  drawn  with  the 
large  compasses.  First  adjust  the 
needle  point  so  that  it  is  a  very 
little  longer  than  the  pencil  point, 
Fig.  11.  Thecompasses,  Fig.  12 
are  manipulated  entirely 
with  the  right  hand. 
They  are  opened  by 
pinching  between  thumb 
and  second  finger  (1), 
and  set  to  proper  radius 
by  placing  the  needle 
point  at  the  center  and 
adjusting  the  pencil  leg 
with  first  and  second  fingers  (2). 
When  the  radius  is  set,  raise  the 
fingers  to  the  handle  (3),  and  re- 
volve the  compasses  by  twirling 
the  handle  between  thumb  and 
finger.  Start  the  arc  near  the 
lower  side  and  revolve  clockwise 
(4),  inclining  the  compasses  in  the 
direction  of  the  line.  Do  not  bore 
a  hole  at  the  center. 

Small  circles  and  arcs  are  drawn 
with  the  bow  pencil.  Adjust  the 
lead  and  the  needle,  and  set  the 
radius  as  shown  in  Fig.  13.  In 
changing  the  bow  instruments 
from  a  small  to  large  radius,  hold 
the  legs  together  with  one  hand 
and  spin  the  nut  with  the  other, 
in  order  to  save  wear  on  the 
threads,  as  shown  at  3,  Fig.  13. 
It  is  also  necessary  to  release  care- 
fully, to  prevent  striking  the  nut 
and  stripping  the  threads.  Always 
be  sure  to  relieve  the  springs  of 
all  the  bow  instruments  when 
putting  them  away. 


10 


MECHANICAL  DRAWING 


11.  Curves  not  circle  arcs  are  drawn  with  the  irregular  or 
" French"  curve.  These  come  in  a  number  of  different  forms 
and  are  shifted  to  fit  the  required  line.  Figure  14  shows  a  line 
being  drawn  by  finding  different  parts  of  the  curve. 

12.  Measuring. — All  measure- 
ments of  lengths  or  distances  on 
a  drawing  are  made  with  the 
scale.  Scales  are  made  with 
different  divisions  for  different 
purposes.  For  machine,  struc- 
tural, and  architectural  drawing 


FIG.   12. — Using  the  compasses. 


FIG.   13. — Using  the  bow  pencil. 


the  mechanical  engineers'  (or  architects')  scale  of  proportional 
feet  and  inches  is  used.  For  school  purposes  the  triangular 
scale,  Fig.  15,  is  much  used,  although  the  flat  shapes  are  preferred 
by  many  draftsmen.  The  symbol  (')  is  generally  used  for  feet 


LEARNING  TO  DRAW 


11 


and  (")  for  inches.     Thus  three  feet  four  and  one-half  inches  is 
written  3'-4K"- 

When  the  object  is  not  too  large  for  the  paper,  it  is  drawn  in 
its  full  size,  using  the  scale  of  inches  and  sixteenths.     To  lay  off 


FIG.  14. — Use  of  the  curve. 


a  full-size  distance,  put  the  scale  down  on  the  paper  against  the 
line  to  be  measured.  Make  a  short  dash  on  the  paper  opposite 
the  zero  on  the  scale  and  another  opposite  the  division  represent- 


- 


'..... 


FIG.  15. — Mechanical   engineers'    (or   architects')   scale. 

ing  the  desired  distance,  Fig.  16.     Do  not  make  a  dot,  or  punch 
a  hole  in  the  paper. 

13.  If  the  object  is  too  large  to  go  on  the  paper  in  its  full  size, 
it  is  drawn  in  reduced  proportion.  The  first  reduction  is  to  the 
scale  of  6"  =  1',  commonly  called  "  half  -size."  To  measure  a 


0  I  2 

FIG.  16. — Marking  a  measurement. 


distance  at  the  scale  of  6"  =  1',  use  the  full-size  scale  and  consider 
each  half-inch  as  representing  an  inch,  each  quarter  inch  as  a 
half-inch,  etc.  Thus  the  12"  scale  will  become  a  24"  scale. 
Example:  To  lay  off  3^"  start  at  the  zero  and  count  three  % 


12 


MECHANICAL  DRAWING 


inches,  and  %  of  the  next  half  inch,  as  shown  in  Fig.  17.     Do 
not  divide  the  size  of  the  piece  by  two. 

If  the  drawing  cannot  be  made  " half-size"  the  next  scale  is 


o 

FIG.   17. — Measuring  to  "half-size." 


3"  =  1',  often  called  "  quarter  size/'  Find  this  scale  and  ex- 
amine it.  The  actual  length  of  three  inches  becomes  one  foot, 
divided  into  12  parts,  each  representing  one  inch,  and  these  are 


FIG.   18. — Reading   the   scale. 

further  divided  into  eighths.  Learn  to  think  of  these  as  real 
inches  in  reduced  scale.  Example :  To  lay  off  the  distance  I'-O^j", 
Fig.  18.  Notice  the  position  of  the  zero  mark,  placed  so  that 


FIG.   19. — Holding  the  dividers. 


inches  are  measured  in  one  direction  from  it  and  feet  in  the 
other,  as  shown  in  the  figure.  Other  scales  found  on  a  trian- 
gular scale  are,  1^"  =  I/;  1"  =  1';  M"  =  1':  V2"  =  l'-,%"  =  1' '; 


LEARNING  TO  DRAW 


13 


Take  each  of  these  scales  in  turn,  and  decide  what  is  the  longest 
distance  that  can  be  measured  in  one  setting,  and  what  is  the 
smallest  division.  Measure  2'-5"  with  each  scale. 

14.  Spacing. — Dividing  lines  into  spaces,  and  transferring  dis- 
tances is  done  with  the  dividers,  or  with  the  bow  spacers.  The 
dividers  are  held  in  the  right  hand  and  adjusted  as  shown  in 


FIG.  20. — Using  the  dividers. 


Fig.  19.  The  method  of  dividing  a  line  into  three  equal  parts  is 
shown  in  the  " movie"  of  Fig.  20.  Adjusting  the  points  of  the 
dividers  until  they  appear  to  be  about  one-third  of  the  length  of 
the  line,  place  one  point  on  one  end  of  the  line,  and  the  other 
point  on  the  line  as  shown  at  (1).  Turn  the  dividers  about  the 
point  which  rests  on  the  line  as  at  (2) ,  then  in  alternate  direction 
as  at  (3).  If  the  last  point  falls  short  of  the  end  of  the  line,  in- 


14 


MECHANICAL  DRAWING 


crease  the  distance  between  the  points  of  the  dividers  by  an 

amount  estimated  to  be  %  of  m-n  and  start  at  the  beginning  of 

the  line  again.     Several  trials  may  be  necessary.     If  the  last 

point  overruns  the  end  of  the  line, 

decrease  the  distance  between  the 

points  by  %  the  extra  distance. 

The  bow  spacers,  Fig.   21,   are 

used  when  working  with  small 

distances. 

15.  It  is  often  convenient  to 
use  the  scale  as  means  of  dividing 
a  line.  If  the  distance  is  not 
easily  divisible,  the  scale  may  be 
used  as  shown  in  the  "  mo  vie" 
of  Fig.  22,  where  (1)  shows  the 
line  which  is  to  be  divided  into 
nine  equal  parts.  Draw  a  per- 
pendicular line  AC  through  an 
end  of  the  line  as  at  (2).  Apply 
the  scale  so  that  nine  divisions 
of  the  scale  (in  this  case  half- 


FIG.  21. 


FIG.  22. — Dividing  a  line. 


inches)  are  included  between  point  B  and  line  AC  as  shown  at  (3). 
Mark  opposite  each  one-half  inch  and  draw  vertical  lines,  which 
will  divide  the  given  line  into  nine  equal  parts  (4).  The  geo- 
metrical method  upon  which  Fig.  22  is  based  is  given  in  Art.  103. 


LEARNING  TO  DRAW 


LETTERING 


15 


16.  Lettering. — The  complete  description  of  a  machine  or 
structure  requires  the  use  of  the  graphical  language  to  describe 
shapes,  and  the  written  language  to  tell  sizes,  methods  of  making, 
kinds  of  materials,  and  other  notes.  The  ''written  language" 
as  used  on  drawings  is  always  in  the  form  of  lettering  and  not 
script  writing.  Simple  freehand  lettering,  perfectly  legible 
and  quickly  made  is  an  important  part  of  modern  engineering 
drawings. 

The  standard  form  of  letter  used  on  working  drawings  is  the 
style  known  as  single-stroke  Gothic.  There  are  two  varieties, 
vertical,  and  inclined.  Some  concerns  use  vertical  letters 
entirely,  some  use  inclined  entirely,  others  use  vertical  for  titles 
and  inclined  for  dimensions  and  notes.  In  the  same  way  some 
schools  adopt  vertical  lettering  as  the  standard,  and  some  adopt 
inclined  lettering.  The  young  draftsman  accepting  a  position 
with  a  company  must  be  able  to  use  the  standard  of  that  com- 
pany. In  learning  both  styles  it  is  better  to  take  up  vertical 
lettering  first. 

The  ability  to  letter  well  and  rapidly  can  be  acquired  only  by  per- 
sistent  and  careful  practice.  The  forms  and  proportions  of  each 


FIG.  23. — Position  for  lettering. 

letter  must  be  thoroughly  mastered  by  study  and  practice,  and 
the  letters  combined  into  uniform  easily  read  words. 

The  term  "single  stroke"  means  that  the  width  of  the  stem  of 
the  letter  is  the  width  of  the  stroke  of  the  pen.  Two  satisfac- 
tory pens  are  Hunt's  512  for  titles  and  large  letters,  and  Gillott's 
404  for  ordinary  dimensions  and  notes.  The  pen  should  be 


16 


MECHANICAL  DRAWING 


held  in  the  position  shown  in  Fig.  23,  the  strokes  drawn  with  a 
steady  even  motion  and  a  slight  uniform  pressure  on  the  paper, 
not  enough  to  spread  the  nibs  of  the  pen.  Lettering  in  pencil 
should  be  done  lightly  with  a  softer  pencil  than  used  for  drawing. 

Guide  lines,  ruled  lightly  with  a  sharp  pencil  should  always 
be  drawn  for  the  tops  and  bottoms  of  each  line  of  letters. 

17.  Single-stroke  Vertical  Capitals. — In  Fig.  24  the  vertical 
capitals  are  arranged  in  " family  order,"  first  the  straight  letters, 


CM  13  IMS 

.J L-J -*i    •  i    f- V    J — ' — 


16 


FIG.  24.  —  Single  stroke  vertical  capitals. 


then  the  slant  line  and  curved  letters.  Each  letter  is  shown  in 
a  square,  so  that  the  proportion  of  its  width  to  height  may  be 
easily  learned.  In  this  style  many  of  the  letters  just  about  fill 
the  square.  The  arrows  and  figures  give  the  order  and  direction 


n  op  eff  s  fill  v  w  xyy  z 

FIG.  25.  —  Single  stroke  vertical  lower  case. 

of  strokes,  which  must  be  learned  for  each  letter.  Vertical 
strokes  are  all  made  downward  and  horizontal  strokes  from  left 
to  right. 

Special  care  and  practice  must  be  given  to  the  numbers.  Notice 
that  the  shapes  of  the  figures  are  just  as  different  from  those 
used  in  ordinary  figuring  as  the  letters  are  from  ordinary  writing  . 


LEARNING  TO  DRAW 


17 


FIG.  26. 


Particularly  is  this  true  of  the  2,  4,  6,  8  and  9.  Fractions  are 
always  made  with  a  horizontal  division  line  with  figures  two- 
thirds  the  height  of  the  whole  numbers  and  a  clear  space  above 
and  below  the  division  line. 

18.  Single-stroke  Vertical  Lower  Case. — Words  lettered  in 
lower  case  or  " small"  letters  are  easier  to  read  than  when  made 

in  capital  letters.  The  single-stroke  lower- 
case alphabet  as  used  with  the  capitals  of 
Fig.  24  is  shown  in  Fig.  25.  These  letters 
are  made  with  bodies  two-thirds  the  height, 
of  the  capitals,  the  ascenders  (6,  d,  f,  etc.) 
extending  up  to  the  cap  line  and  the  descenders  (g,  p,  q,  etc.) 
dropping  the  same  distance  below.  They  are  based  upon  the 
combination  of  circle  and  straight  line,  Fig.  26.  The  " mono- 
gram" in  the  figure  contains  eighteen  of  the  twenty-six  letters. 

19.  Single-stroke  Inclined  Caps. — In  making  inclined  letters 
there  are  two  things  to  watch, 

first,  to  keep  a  uniform  slope, 
second,  to  get  the  rounded  let- 
ters of  the  correct  shape. 

Slanting  ' '  direction  lines ' ' 
should  be  drawn  either  with  a 
lettering  triangle  (of  about 
67J^°)  or  by  setting  a  slope  of 
2  to  5  by  marking  two  units  on 
a  horizontal  line  and  five  on  a 
vertical  line,  and  using  T-square 
and  triangle  as  shown  in  Fig.  27. 

The  form  taken  by  the  rounded  letters  when  inclined  is  illus- 
trated in  Fig.  28,  showing  that  the  curves  are  sharp  in  the  upper 
right-hand  and  lower  left-hand  corners  and  flattened  in  the 
other  two  corners. 


FIG.  27. 


FIG.  29. 


The  letters  H,  A,  V  and  W  are  shown  enlarged  in  Fig.  29. 
Note  particularly  that  the  lines  of  A,  V  and  W  must  make  equal 
angles  on  each  side  of  the  sloping  direction  lines. 

The  alphabet  and  numerals  are  given  in  family  order  in  Fig.  30. 


18 


MECHANICAL  DRAWING 


20.  Single-stroke  Inclined  Lower  Case. — This  letter,  some- 
times called  the  Reinhardt  letter,  is  in  general  use  for  notes  on 
drawings  as  it  is  very  legible  and  effective  and  can  be  made  very 
rapidly.  The  bodies  are  two-thirds  the  height  of  the  capitals, 


TL 


f  A//-  A/4 


/f^*  /^J'  ^    ^D    trlii  '//T    " 

o  ©  a  <s  w  & 


FIG.  30. — Single  stroke  inclined  capitals. 

with  the  ascenders  extending  to  the  cap  line,  and  the  descenders 
dropping  the  same  distance  below  the  base  line. 

For  study,  the  letters  may  be  divided  into  four  groups: 

Group  I,ijkltvwxyz 

Group  II,  a  b  d  /  g  p  q 

Group  III,  h  m  n  r  u  y 

Group  IV,  c  e  o  s 


FIG.  31. 


FIG.  32. 


Group  I  contains  the  straight  letters.  Be  particularly  careful 
about  the  slant  of  the  angle  letters  v  w  x  y  and  z. 

The  letters  of  Group  II  are  made  up  of  a  partial  ellipse  whose 
axis  slants  45  degrees,  and  an  inclined  straight  line,  Fig.  31. 
The  hook  letters  of  Group  III  are'  made  with  a  part  of  the  same 
ellipse.  The  monogram  of  Fig.  31  illustrates  this  group  also. 


LEARNING  TO  DRAW 


19 


The  letters  of  Group  IV  are  made  with  the  same  ellipse  as  the 
capitals,  Fig.  32. 

The  alphabet  with  order  and  direction  of  strokes  is  given  in 
Fig.  33. 


&  t  tt'&  f?ft  i  k/'ffi 


fuv  wxyz 

FIG.  33.  —  Single  stroke  inclined  lower  case. 

21.  Composition.  —  Composition  in  lettering  means  the  selec- 
tion of  appropriate  styles  and  sizes  of  letters,  and  their  arrange- 
ment and  spacing.  After  the  shapes  of  the  separate  letters  have 

LETTERING  COMPOSITION 
involves  the  spacing  of  letters  in  words. 
the  spacing  of  words  and  lines,  and  the 
choice  of  appropriate  styles  and  sizes. 

FIG.  34.  —  An  example  of  spacing. 

been  mastered  the  entire  practice  should  be  on  words  and  sen- 
tences.   Letters  in  words  are  not  spaced  at  equal  distances  along 


FIG.  35. — Spacing  guide  lines. 

the  guide  lines,  but  so  that  the  areas  of  white  spaces  between  the 
letters  are  approximately  equal,  making  them  appear  to  be  spaced 
uniformly.  Figure  34  is  an  illustration  of  composition. 


20  MECHANICAL  DRAWING 

In  spacing  words  the  clear  distance  between  them  should  be 
about  equal  to  the  height  of  the  letters.  The  clear  distance  be- 
tween lines  varies  from  one-half  to  one  and  one-half  times  the 
height  of  the  caps.  Figure  35  illustrates  a  method  of  spacing  guide 
lines  for  tops  and  bottoms  when  several  lines  of  letters  are  to  be 


ABCDEFGH1JKLMN 

OPQJISTUVWXYZ&' 

1234567890 

abcdefthijklmnopqrjtuvwxyz 


FIG.  36. — Single  stroke  Roman. 

made.  Mark  the  height  of  the  letter  on  the  first  line,  then  set 
the  dividers  to  the  distance  wanted  between  base  lines  and 
step  off  the  required  number  of  lines.  With  the  same  setting 
step  down  again  from  the  upper  point. 

The  composition  of  titles  is  referred  to  in  Art.  68.  An  alpha- 
bet of  single-stroke  Roman  letters  for  use  in  architectural  draw- 
ing is  given  in  Fig.  36. 


CHAPTER  III 


THEORY  OF  SHAPE  DESCRIPTION 

22.  There  are  two  things  which  a  designer,  inventor  or  builder 
must  be  able  to  do;  first,  he  must  be  able  to  visualize,  or  to  see 
clearly  in  his  mind's  eye  what  an  object  looks  like  without  actually 
having  the  object;  second,  he  must  be  able  to   describe  it  so 
that  it  could  be  built.     A  few  lines  properly  drawn  on  paper  will 
describe  an  object  more  accurately  and  clearly  than  a  picture 
or  a  written  description.     To  describe  the  true  shape  of  an  object 
by  means  of  lines,  and  to  be  able  to  read  and  understand  such 
descriptions  requires  a  thorough  knowledge  of  the  theory  upon 
which  this  method  is  based. 

23.  Describing  Objects  by  Views. — For  the  graphical  description 
of  an  object  we  have  available  the  paper,  pencil  and  instruments 

explained  in  Chapter  II.  On  the 
paper  we  can  make  measurements 
in  a  single  plane  only,  while  all 
objects  have  dimensions  perpen- 
dicular to  the  paper  as  well  as 
parallel  to  it.  A  picture  can  be 


FIG.  37. 


FIG.  38.— Top   view. 


made  which  would  show  just  as  a  photograph  would  do, 
the  general  appearance  of  the  object,  but  it  would  not  show 
the  exact  forms  and  relations  of  the  parts  of  the  object.  It  would 
show  it  as  it  appears  and  not  as  it  really  is. 

Our  problem  then  is  to  represent  solid  objects  on  a  flat  sheet 
of  paper  in  such  a  manner  as  to  tell  the  exact  shape.  This  is 
done  by  drawing  a  system  of  "views"  of  the  object  as  seen  from 
different  positions,  and  arranging  these  views  in  a  definite  manner. 

A  picture  of  a  telephone,  Fig.  37,  shows  the  instrument  as  it 

21 


22 


MECHANICAL  DRAWING 


ordinarily  appears  to  us,  but  it  does  not  show  the  true  shapes  of 
the  parts.  The  base  appears  as  an  ellipse,  although  we  know  that 
it  really  is  circular.  If  we  look  down  at  the  instrument  from 
directly  above  we  obtain  a  view  showing  the  exact  shape  of  the 
base,  and  the  outline  of  the  other  parts  as  seen  from  above.  This 
is  called  a  top  view  or  plan,  Fig.  38.  This  view  does  not  tell  us 
the  height  of  the  instrument,  so  it  is  necessary  to  take  another 
view  from  a  position  directly  in  front  or  else  from  the  left  or 
right  side.  In  this  way  either  a  front  view  or  side  view  to  show  the 


FIG.  39. — The~  three  views. 

height,  is  added,  Fig.  39.  Often,  as  in  this  case,  both  front  view 
and  side  view  in  addition  to  top  view  are  needed  to  describe  the 
object. 

Since  the  bottom  of  the  base  is  level  it  will  show  as  a  straight 
line  in  the  front  and  side  views,  as  will  the  bottom  of  the  receiver 
and  all  other  horizontal  circles.  The  front  view  shows  the 
circular  shape  of  the  transmitter,  while  the  side  view  shows  the 
true  shape  of  the  connection  between  transmitter  and  post. 

The  three  views  taken  together  completely  define  the  shapes 
of  all  the  parts  of  the  instrument  and  their  exact  relations  to 
each  other. 


THEORY  OF  SHAPE  DESCRIPTION 


23 


It  is  evident  that  the  front  and  side  views  are  exactly  the  same 
height.  When  drawn  they  are  placed  directly  across  from  each 
other.  The  top  view  is  placed  directly  above  the  front  view, 
and  the  three  views  together  appear  as  in  Fig.  39. 

Sometimes  a  left  side  view  describes  the  object  more  clearly 
than  the  right  side  would  do.  Fig.  40  shows  the  top,  front  and 
left  side  views. 

Notice  in  Figs.  39  and  40  that  the  mouthpiece  is  toward  the 
front  in  the  top  views,  and  also  toward  the  front  view  in  both 
the  right  and  left  side  views. 


FIG.  40. — Top,  front  and  left  side  views. 

As  a  further  explanation  of  the  relation  of  the  three  views, 
study  the  drawing  of  the  chair  shown  in  Fig.  41.  Notice  that 
the  magazine  holder  is  at  the  right  in  the  top  and  front  views 
and  therefore  shows  in  the  right  side  view.  The  front  of  the 
chair  is  toward  the  front  view  in  the  top  and  two  side  views. 

24.  Theory  of  the  Relation  of  Views. — The  principle  of  repre- 
senting an  object  by  different  views,  as  just  described,  is  called 
Orthographic  Projection,  and  is  the  basis  of  all  kinds  of  industrial 
drawing.  The  real  theory  of  orthographic  projection  must  be 
well  understood  before  complicated  or  difficult  drawings  can  be 
made  or  read. 


24 


MECHANICAL  DRAWING 


The  following  definition  has  been  given:  "Orthographic  pro- 
jection is  the  method  of  representing  the  exact  form  of  an  object  in 
two  or  more  views  on  planes  generally  at  right  angles  to  each  other, 
by  dropping  perpendiculars  from  the  object  to  the  planes" 


FIG.  41. — Relation   of   views. 


Suppose  the  book  end  shown  in  Fig.  42  is  to  be  represented. 
The  draftsman  imagines  himself  to  be  looking  through  a  trans- 
parent plane  set  up  in  front  of  the  object,  Fig.  43.  If  from  every 
point  of  the  object  perpendiculars  be  imagined  as  extended  or 


FIG.  42. 


FIG.  43. — The   vertical   plane. 


projected  to  the  plane,  the  result  on  the  front  of  the  plane  would 
be  the  projection  on  the  plane,  called  the  vertical  projection,  or 
front  view,  or  in  architectural  drawing  the  front  elevation;  and 
would  show  the  true  height  and  length  of  the  object. 


THEORY  OF  SHAPE  DESCRIPTION 


25 


Suppose  now  that  a  horizontal  plane  is  hinged  at  right  angles 
to  the  first  plane,  the  observer  looking  through  it  at  the  top  of 
the  object.  Perpendiculars  from  the  object  to  this  plane  will 
give  the  horizontal  projection,  or  top  view,  or  as  called  in  architec- 


FIG.  44.— The  glass   box. 


tural  drawing,  the  plan.     This  view  will  show  the  width  of  the 
object  from  front  to  back,  as  well  as  the  length  already  shown  on 


FIG.  45. — The  box  opened. 

the  front  view.  These  two  planes  represent  the  drawing  paper, 
and  if  the  horizontal  plane  be  imagined  as  swung  up  on  the  hinges 
until  it  lies  in  the  extension  of  the  front  plane,  the  two  views  will 
be  shown  in  their  correct  relationship  as  they  would  be  drawn  on 
the  paper,  and  together  give  the  length,  breadth  and  height. 
This  explains  the  reason  for  the  statement  made  in  the  preceding 
section,  that  the  top  view  is  always  drawn  directly  over  the  front 
view. 


26 


MECHANICAL  DRAWING 


The  side  view  or  side  elevation  is  imagined  as  made  on  a  plane 
perpendicular  to  both  top  and  front  planes.  Thus  the  object 
may  be  thought  of  as  being  inside  of  a  glass  box,  or  show  case, 
as  in  Fig.  44.  The  projections  on  the  sides  of  this  box  would  be 


FIG.  46. 


FIG.  47. 


the  views  which  we  have  discussed,  and  when  these  sides  are 
opened  up  into  one  plane,  the  views  take  their  relative  positions 
as  on  the  paper,  with  the  top  view  directly  over  the  front  view 
and^the  side  views  directly  across  from  the  front  view,  Fig.  45. 


FIG.  48. 


FIG.  49. 


25.  From  a  study  of  these  projections  the  following  principles 
will  be  noted: 

1.  A  face  parallel  to  a  plane  of  projection  is  shown  in  its  true  size, 
as  A  on  the  front  view,  Fig.  43. 

2.  A  face  perpendicular  to  a  plane  of  projection  is  projected  as 
a  line;  as  B  and  C,  Fig.  43. 


THEORY  OF  SHAPE  DESCRIPTION 


27 


3.  A  surface  inclined  to  a  plane  of  projection  shows  foreshortened, 
as  B,  Fig.  48. 

Similarly — 

4.  A  line  parallel  to  a  plane  of  projection  will  show  in  its  true 
length. 


FIG.  50. 


FIG.  51. 


5.  Aline  perpendicular  to  a  plane  of  projection  will  be  projected  as 
a  point. 

6.  An  inclined  line  will  have  a  projection  shorter  than  its  true 
length. 


FIG.  52. 


FIG.  53. 


26.  As  a  further  explanation  of  how  the  theory  of  projection 
is  applied,  study  the  drawings  of  the  objects  in  the  following 
figures.  In  Fig.  46  each  view  represents  a  single  surface.  In 
Fig.  47  the  top  view  shows  two  surfaces  A  and  B  at  different 
levels,  and  as  shown  by  the  front  view,  surface  A  is  above  surface 
B.  In  the  side  view  the  surfaces  C  and  D  are  shown.  In  Fig. 
48  the  surface  B  is  inclined  and  shows  slightly  foreshortened  in 


28 


MECHANICAL  DRAWING 


the  top  view  and  very  much  foreshortened  in  the  side  view.  To 
obtain  the  true  size  of  the  surface  B,  its  length  must  be  taken 
from  the  front  view  and  its  width  from  the  top  or  side  view.  A 
surface  which  is  inclined  in  three  ways  is  illustrated  in  Fig.  49 
where  the  corner  of  the  block  has  been  cut  away. 

27.  Since  it  is  necessary  to  describe  every  part  of  an  object, 
all  surfaces  must  be  represented  whether  they  can  actually  be 


^!i!i!!!^ 


FIG.  54. 

seen  or  not.  To  distinguish  surfaces  which  cannot  be  seen  in 
the  views,  they  are  represented  by  dotted  lines  as  in  Figs.  50, 
51  and  52.  Notice  that  a  dotted  line  touches  the  line  from  which 
it  starts,  that  dots  touch  at  corners,  but  that  if  a  dotted  line  is 
the  continuation  of  a  full  line,  a  space  is  left  between  the  full 
line  and  the  first  dot  of  the  dotted  line. 


FIG.  55. 


FIG.  56. 


FIG.  57. 


28.  The  fact  that  curved  surfaces  do  not  show  as  curves  in  all 
views  is  illustrated  in  Figs.  53  and  54.  A  cylinder  appears  as  a 
circle  in  one  view  and  as  a  rectangle  in  the  others,  as  in  Figs. 
55,  56  and  57,  which  show  three  views  of  a  cylinder  when  placed 
in  different  positions. 

Figure  58  shows  a  bearing  made  up  of  flat  and  curved  surfaces 
and  requiring  visible  and  invisible  lines.  Note  that  surface  A 
of  the  side  view  is  shown  by  a  full  line  a-a  in  the  front  view  and 
by  a  dotted  line  a-a'  in  the  top  view. 


THEORY  OF  SHAPE  DESCRIPTION 


29 


FIG.  58. — A  bearing. 


FIG.  61. 


FIG.  62. 


30 


MECHANICAL  DRAWING 


Pictures  and  drawings  of  several  objects  are  given  in  Figs.  59 
to  64  for  study  and  comparison. 

29.  Freehand  Studies. — In  Fig.  65  is  shown  the  picture  of  an 
overhanging  V  block,  and  in  Fig.  66  a  freehand  sketch  in  pencil 


FIG.  63. 


FIG.  64. 


of  the  views  required  for  describing  its  shape.  The  objects 
shown  in  Figs.  67  and  68  are  designed  to  give  the  pupil  practice 
in  shape  description  by  freehand  sketching  either  in  pencil  on 


FIG.  65. — V  block,  to  be  sketched. 

plain  or  squared  paper,  or  on  the  blackboard.  The  necessary 
views  of  selected  objects  are  to  be  blocked  in  and  brightened  as  in 
Fig.  66.  The  pictures  are  not  to  be  copied. 


THEORY  OF  SHAPE  DESCRIPTION 


31 


32 


MECHANICAL  DRAWING 


FIG.  67. — Problems  for  freehand  sketching. 


THEORY  OF  SHAPE  DESCRIPTION 


33 


FIG.  68. — Problems  for  freehand  sketching. 


34 


MECHANICAL  DRAWING 


30.  Sections. — We  have  learned  that  parts  of  an  object  which 
cannot  be  seen  are  represented  by  dotted  lines,  and  this  method 
is  satisfactory  where  the  object  is  solid  or  the  interior  simple. 
There  are  many  cases,  especially  if  there  is  considerable  interior 
detail,  or  if  several  pieces  are  shown  together,  when  the  dotted 
lines  become  confusing  or  hard  to  read.  This  difficulty  is  avoided 
by  using  a  sectional  view. 


FIG.  69. — Cutting  plane. 


FIG.     70. — Object     after    front    half 
removed. 


A  sectional  view  is  a  view  obtained  by  supposing  the  piece  to 
be  cut  apart  and  the  front  portion  removed,  thus  exposing  the 
interior,  as  shown  in  pictorial  form  in  Figs.  69  and  70,  and  by 
views  in  Fig.  71. 

The  plane  of  the  cut  surface  is  shown  extended  in  Fig.  69.  In 
Fig.  70  we  imagine  that  the  part  of  the  object  in  front  of  the  plane 


— 

—  f-  1—  - 

FIG.  71. — Sectional  view. 

has  been  removed.  In  Fig.  71  the  cut  surface  is  indicated  by 
cross-hatching,  or  section  lining,  with  uniformly  spaced  fine  lines, 
which  are  generally  drawn  at  a  slope  of  45  degrees.  In  "the  top 
view  the  position  of  the  cutting  plane  is  indicated  by  a  line  (see 
alphabet  of  lines,  Art.  62)  but  the  part  supposed  to  be  cut  away 
is  not  left  out.  Study  each  piece  shown  in  Fig.  72  until  the  reason 
for  every  line  is  clear. 


THEORY  OF  SHAPE  DESCRIPTION 


35 


The  cutting  plane  need  not  be  continuous  but  may  be  taken 
so  as  to  show  any  desired  details  of  the  interior. 


FIG.  72. — Sections  for  study. 


FIG.  73.— A  half  section. 


A  full  section  is  the  view  obtained  when  the  cutting  plane  ex- 
tends clear  through  the  object,  whether  continuous  or  not, 
Fig.  71. 


36 


MECHANICAL  DRAWING 


A  half  section  is  a  view  obtained  when  the  cutting  plane  ex- 
tends only  halfway  through  the  piece,  that  is  when  one  quarter 
of  the  piece  is  imagined  to  have  been  removed,  Fig.  73.  This 
method  is  used  to  advantage  when  a  machine  or  construction  is 
symmetrical,  as  it  shows  both  the  interior  and  the  exterior.  The 
dotted  lines  are  generally  left  out  on  both  sides  of  the  center  line. 


FIG.  74. 

For  simple  pieces  all  lines  beyond  the  plane  of  the  section, 
both  full  and  dotted  are  drawn. 

Any  piece  must  have  the  section  lines  in  the  same  direction 
on  all  parts  of  its  cut  surface.  When  two  pieces  are  shown  to- 
gether they  are  sectioned  in  different  directions,  Fig.  74. 


FIG.  75. — Bolts,  shafts,  etc.,  on  sectional  views. 

It  is  not  necessary  to  cut  through  all  the  parts  of  a  machine. 
Such  parts  as  bolts,  nuts,  screws,  keys,  shafts,  etc.,  are  not  sec- 
tioned, Fig.  75. 

Different  materials  are  sometimes  indicated  by  varying  the 
kinds  of  section  lines  and  the  spacing  between  them.  A  system 
for  this  purpose  is  shown  in  Fig.  159,  page  81.  As  there  are 


THEORY  OF  SHAPE  DESCRIPTION 


37 


other  standards,  such  symbols  should  not  be  depended  upon  alone 
as  a  means  of  specifying  the  material.  Always  use  a  note  for 
this  purpose. 

The  spacing  of  section  lines  should  be  such  as  will  give  the 
effect  of  an  even  tint.  For  most  purposes  the  distance  between 
lines  is  about  inch,  spaced  entirely  by  eye.  Uneven  spacing 


FIG.  76. — An  auxiliary  view. 

will  ruin  the  appearance  of  a  drawing  and  make  it  harder  to  read. 
Very  small  pieces  require  somewhat  closer  spacing  than  large 


ones. 


FIG.  77. 


FIG.  78. 


FIG.  79. 


31.  Auxiliary  Views.— We  have  found,  Art.  26,  Fig.  48,  that 
slanting  surfaces  are  foreshortened  when  represented  in  the  usual 
views.  It  is  sometimes  necessary  or  desirable  to  show  a  slanting 
surface  in  its  true  shape,  especially  when  it  has  an  irregular  out- 
line. Such  a  view  can  be  drawn  by  looking  directly  at  the  slant- 
ing surface.  When  this  is  done  all  the  regular  views  do  not  have 
to  be  drawn,  Fig.  76. 


38 


MECHANICAL  DRAWING 


The  object  shown  in  Fig.  77  would  ordinarily  be  drawn  as  in 
Fig.  78,  obtaining  the  side  view  by  looking  in  the  direction  of 
arrow  I.  The  face  A,  does  not  show  in  its  true  size  in  Fig.  78. 
However,  if  we  look  in  the  direction  of  arrow  II  perpendicular  to 
face  A  the  object  would  be  drawn  as  in  Fig.  79,  and  instead  of  the 
usual  side  view  we  would  have  an  auxiliary  view  placed  as  shown, 
and  giving  the  true  size  and  shape  of  face  A.  The  auxiliary  view 
of  Fig.  77  has  thus  been  made  on  an  auxiliary  plane  parallel  to 
face  A,  Fig.  79. 

When  making  working  drawings  for  practical  use,  the  whole 
object  is  not  generally  projected,  part  views  being  used  instead  as 
in  Fig.  80. 


FIG.  80. — An  auxiliary  part  view. 


32.  The  usual  method  of  drawing  an  auxiliary  view  is  by  mak- 
ing use  of  a  center  line.  To  obtain  an  auxiliary  view  of  the  cut 
surface  of  the  hexagonal  prism,  Fig.  81,  draw  a  horizontal  center 
line  in  the  top  view  and  another  center  line  parallel  to  the  cut 
face  at  any  convenient  distance  from  it.  Draw  projecting  lines 
perpendicular  to  the  cut  face  from  each  point.  On  each  of  these 
lines  locate  points  by  measuring  on  each  side  of  the  auxiliary 
center  line,  distances  obtained  from  the  top  view.  Distances 
a  and  6  are  toward  the  front  of  the  object  as  shown  in  the  top 
view  and  therefore  are  measured  toward  the  front  in  the  auxiliary 
view.  In  Fig.  82  the  entire  object  has  been  projected  to  the 
auxiliary  plane,  using  the  method  just  described. 

The  auxiliary  view  of  the  cut  surface  of  a  cylinder  is  shown  in 
Fig.  83.  In  this  case  the  vertical  center  line  of  the  end  view 


THEORY  OF  SHAPE  DESCRIPTION 


39 


corresponds  with  the  inclined  center  line.  Select  a  convenient 
number  of  points  on  the  front  view  of  the  inclined  surface  and 
draw  perpendiculars  from  them  to  the  parallel  center  line. 
Locate  the  points  in  the  end  view  by  projecting  from  the  front 


FIG.  81. 


FIG.  82. 


view,  thus  obtaining  the  distances  to  measure  toward  the  front 
or  back  from  the  inclined  center  line. 


FIG.  83. 

Similar  methods  are  used  for  obtaining  the  auxiliary  projec- 
tions of  cones,  pyramids  and  other  objects. 

33.  Revolutions. — It  is  generally  possible  to  place  an  object 
in  a  simple  position  so  that  most  of  its  lines  show  in  their  true 
length  or  can  be  easily  located  on  the  planes  of  projection.  Ordi- 
narily, drawings  are  made  in  this  way.  However,  it  is,  of  course, 
possible  to  represent  an  object  tipped  about  one  of  its  edges  or 
resting  on  one  of  its  corners.  To  obtain  the  views  of  an  object 


40 


MECHANICAL  DRAWING 


in  such  an  unnatural  position  draw  it  first  in  its  natural  position, 
then  revolve  to  the  new  position  about  one  or  more  imaginary 
axes  taken  perpendicular  to  the  planes  of  projection. 


FIG.  84. — Revolutions. 


FIG.  85.      . 


FIG.  86. — Double  revolution. 


At  A  in  Fig.  84  we  have  two  views  of  an  object  in  a  natural 
position.  Suppose  a  hole  is  drilled  through  from  the  front  and 
a  shaft  inserted  as  shown.  The  object  might  be  revolved  about 
the  shaft  or  axis  into  a  new  position  as  at  B.  It  will  be  observed 


THEORY  OF  SHAPE  DESCRIPTION 


41 


42  MECHANICAL  DRAWING 

that  the  front  view  of  B  is  the  same  as  the  front  view  of  A  except 
that  its  position  has  been  changed.  The  top  view  of  B  is  ob- 
tained by  projecting  up  from  the  new  front  view,  and  across 
from  the  top  view  of  A.  The  rule  of  revolution  may  now  be 
stated : 

First. — The  view  perpendicular  to  the  axis  of  revolution  is  un- 
changed except  in  position.  Second. — Distances  parallel  to  the 
axis  of  revolution  are  unchanged. 

In  Fig.  85  the  method  of  drawing  an  object  when  revolved 
about  a  vertical  axis  is  shown.  Given  the  two  views  as  at  A,  it 
is  required  to  draw  three  views  after  the  piece  has  been  revolved 
through  30°  about  a  vertical  axis.  First  draw  the  top  view 
in  its  new  position,  B.  Since  the  axis  is  vertical,  the  height 
has  not  been  changed,  so  a  horizontal  projecting  line  may  be 
drawn  from  point  1,  of  A  and  a  vertical  projecting  line  from  the 
top  view  of  B.  The  intersection  of  the  two  lines  just  drawn  will 
locate  'the  position  of  point  1  in  the  new  front  view.  Proceed 
in  the  same  way  for  each  point  and  join  the  points  to  complete 
the  view.  The  side  view  is  obtained  from  the  front  and  top  views 
in  the  usual  manner. 

After  an  object  has  been  revolved  about  an  axis  perpendicular 
to  a  plane  it  may  'be  revolved  about  an  axis  perpendicular  to 
another  plane.  This  is  double  or  successive  revolution  and  is 
illustrated  in  Fig.  86,  where  the  piece  has  been  revolved  about  a 
vertical  axis  through  30°,  and  from  this  position  about  an  axis 
perpendicular  to  tne  vertical  plane  through  45°. 

An  object  may  be  revolved  to  the  right- or  to  the  left  about  an 
axis  perpendicular  to  the  horizontal  or  vertical  plane,  or  it  may 
be  revolved  forward  or  backward  about  an  axis  perpendicular 
to  the  profile  or  side  plane.  The  various  positions  are  illustrated 
in  Fig.  87.  The  view  which  is  unchanged  in  size  and  shape  is 
shown  slightly  tinted  in  each  case. 

PICTORIAL  DRAWING 

34.  Pictorial  Drawing. — Thus  far  we  have  studied  shape  de- 
scription by  the  exact  method  of  separate  views,  or  orthographic 
projection.  In  addition  to  a  knowledge  of  this  method  it  is 
very  necessary  for  a  draftsman  to  be  able  on  occasion  to  make  a 
pictorial  view,  either  freehand  or  with  instruments. 

By  those  familiar  with  the  subject,  sketches  are  often  made 
in  perspective,  showing  the  object  as  it  would  actually  appear  to 


THEORY  OF  SHAPE  DESCRIPTION 


43 


the  eye.,  An  easier  way,  although  the  result  is  not  so  pleasing 
in  appearance  as  a  well-made  perspective,  is  to  use  one  of  the 
pictorial  methods  of  projection,  of  which  the  commonest  are 
isometric  drawing,  oblique  drawing,  and  cabinet  drawing.  These 
all  show  three  faces  in  one  view  and  have  the  advantage  that  the 
principal  lines  can  be  measured  directly.  While  similar  in  effect, 
these  three  methods  must  not  be  confused. 

35.  Isometric  Drawing. — This  simple  method  is  based  on 
revolution,  Fig.  88.  If  a  cube  be  imagined  as  tilted  up  on  one 
corner  to  such  an  angle  that  its  front  view  shows  three  faces 
equal  in  shape  and  size  it  is  said  to  be  in  isometric^  projection. 


Isomefr/c  Pruning 


FIG.  88.— The  isometric  cube. 


In  this  position  the  edges  would  evidently  not  show  in  their  true 
length.  An  isometric  drawing  of  the  same  cube  is  the  same  shape 
but  a  little  larger  in  size  as  the  edges  are  drawn  in  their  true 
length  instead  of  in  the  foreshortened  length. 

Isometric  drawings  are  thus  built  on  a  skeleton  of  three  lines 
^presenting  the  three  edges  of  the  cube.  These  three  lines  form 
three  equal  angles  of  120°  and  are  called  the  isometric  axes. 
One  is  drawn  vertically,  the  others  with  the  30°  triangle  as 
shown  in  Fig.  89.  The  intersection  of  these  lines  would  be  the 
front  corner  of  a  block  with  -square  corners.  Measuring  the 
length,  breadth  and  thickness  of  the  block  on  the  three  axes,  and 
drawing  through  these  points  lines  parallel  to  the  axes  will  give 
the  isometric  drawing  of  the  block.  It  is  often  better  to  start 
with  the  axes  in  the  " second  position,"  representing  the  lower 
corner  as  in  Fig.  90. 

Any  line  on  the  object  parallel  to  one  of  these  edges  is  drawn 
parallel  to  it  and  is  called  an  isometric  line.  The  first  rule  of 

1  Isometric — equal  measure. 


44 


MECHANICAL  DRAWING 


isometric  drawing  is:  Measurements  can  be  made  only  on  iso- 
metric lines.  The  second  rule  is:  Remember  the  isometric  cube. 
36.  Non-isometric  Lines. — Lines  not  parallel  to  one  of  the 
isometric  axes  are  called  non-isometric  lines.  Such  lines  will 
not  show  in  their  true  length  and  cannot  be  measured,  but  must 
be  drawn  by  locating  their  two  ends. 


\ 
1 

FIG.  89. — Isometric  axes.     First  position. 


FIG.  90. — Isometric  axes.     Second   position. 


G       B 
FIG.   91. — Construction  for  non-isometric  lines. 

37.  Angles  between  lines  on  isometric  drawings  do  not  show 
in  their  true  size,  and  cannot  be  measured  in  degrees.  All  the 
angles  of  a  cube  are  right  angles  but  in  the  isometric  drawing 
some  would  measure  120°  and  some  60°.  In  drawing  angles  other 
than  90°,  the  lines  forming  them  must  be  transferred  from  the 
orthographic  views  as  shown  in  Fig.  91.  To  make  an  iso- 


THEORY  OF  SHAPE  DESCRIPTION 


45 


metric  drawing  of  the  packing  block  shown  at  I,  first  drop  per- 
pendiculars on  the  front  view  from  the  points  D  and  E,  giving 
the  construction  lines  DF  and  EG.  Then  draw  the  two  isometric 
axes,  AB  and  AC  as  at  II,  and  measure  the  distances  AF  and 
BG.  Draw  vertical  lines  at  F  and  G  equal  to  the  corresponding 
lines  in  the  front  view.  The  non-isometric  lines  AD  and  BE 
can  then  be  drawn  and  the  angles  at  A  and  B  will  be  represented 
correctly.  Finish  the  figure  as  at  III. 


FIG.  92. — Construction  of  isometric  circle. 

38.  Circles  will  appear  as  ellipses  in  isometric  drawing,  but 
instead  of  drawing  a  true  ellipse  a.  fonr-gpntered  apprflriflna.t.inTi 
is  usually  made.  To  draw  an  isometric  circle,  first  make  the 
isometric  drawing  of  the  square  which  will  contain  it,  Fig.  92. 
From  the  points  of  tangency  draw  perpendiculars.  Their  inter- 


Orthograph/c 


FIG.  93. — Isometric  arcs. 


FIG.  94. — Isometric  half-section. 


sections  will  give  four  centers  for  arcs  tangent  to  the  sides  of  the 
square.  Two  of  these  centers  will  fall  at  the  corners  of  the  square, 
as  shown  at  II.  Thus  the  entire  construction  may  be  made  with 
the  60°  triangle.  The  construction  for  quarter  rounds  is  the 
same,  as  shown  in  Fig.  93,  where  the  radius  is  measured  from 
the  corner  and  actual  perpendiculars  of  90°  drawn  to  find  the 
required  center. 

39.  Sections. — Isometric  drawings  are  generally  made  as  out- 
side views,  but  sometimes  a  sectional  view  is  needed.  The  sec- 
tion is  taken  on  an  "isemetric  plane,"  that  is,  on  a  plane  parallel 


46 


MECHANICAL  DRAWING 


to  one  of  the  faces  of  the  cube.     Figure  94  shows  a  half  section 
and  Fig.  95  a  full  section  of  the  same  piece. 

40.  Making  an  Isometric  Drawing. — Problem:  Make  an 
isometric  drawing  of  the  guide,  Fig.  96.  First,  draw  the  axes 
AB,  AC  and  AD,  in  second  position,  Fig.  97. 

Measure  from  A}  the  length  3"  on  AB 

Measure  from  A,  the  width  2"  on  AC 

Measure  from  A,  the  thickness  %"  on  AD 


FIG.  95. — Isometric  section. 


FIG.  96. — Problem  for  isometric  drawing. 


Through  these  points  draw  isometric  lines,  blocking  in  the  base. 
Second,  block  in  the  upright,  making  two  measurements  only, 
2"  and  %".  Third,  locate  center  of  hole,  and  draw  its  center 
lines  as  shown.  Block  in  a  24"  isometric  square  and  draw  the  hole 


FIG.  97.— First    stage. 


FIG.  98.— Second  stage. 


as  an  approximate  ellipse  by  Art.  38.  At  the  upper  corners 
measure  the  one-half  inch  radius  on  each  line,  Fig.  98,  and  draw 
real  perpendiculars  to  find  the  centers  of  the  quarter  circles. 
Fourth,  finish  the  drawing  as  'in  Fig.  99. 

41.  Making  a  Freehand  Isometric  Drawing. — Freehand  iso- 
metric sketches  are  of  great  help  in  reading  orthographic  views 

V 


THEORY  OF  SHAPE  DESCRIPTION 


47 


and  in  explaining  objects  or  parts  of  construction.  The  princi- 
ples of  isometric  drawing  form  the  basis  of  isometric  sketching, 
but  since  sketches  arg  not  made  to  scale,  their  appearance  'is 
improved  by  flattening,  that  is,  giving  the  axes  an  angle  less  than 
30°  with  the  horizontal,  and  by  slightly  converging  the  lines, 
as  well  as  foreshortening  the  lengths,  thus  avoiding  the  distortion 
and  giving  the  effect  of  perspective. 
This  is  sometimes  called  "fake  per- 
spective." 

Always  block  in  construction  squares 
before  sketching  circles  or  arcs,  and 
remember  that  the  long  axes  of 
ellipses  representing  circles  on  the 
top  face  are  horizontal. 

42.  Oblique  Drawing.— This  form 
of  pictorial  drawing  is  based  upon 
the  theoretical  principle  that  the  ob- 
ject is  placed  parallel  to  the  plane  of  projection  and  projected 
to  it  by  oblique  projecting  lines  instead  of  perpendicular  ones. 
Practically  it  is  drawn  on  three  axes,  just  as  isometric,  but  two 
of  the  axes  always  make  right  angles  with  each  other,  that  is, 
one  axis  is  drawn  vertically,  one  horizontally  and  the  third  at 
any  convenient  angle,  Fig.  100. 


60* to  right  reversed 


FIG.  99. — Completed  "drawing. 


30"  to  right 


45*  to  left  60" to  right 

FIG.   100. — Axes  in  oblique  drawing. 


The  same  methods  and  rules  as  used  in  isometric  apply  to  ob- 
lique, but  compared  with  isometric  it  has  the  distinct  advantage 
of  showing  one  face  without  distortion.  Thus  objects  with 
irregular  outlines  can  be  drawn  by  this  method  much  more  easily 
and  effectively  than  in  isometric,  and  many  draftsmen  prefer  it 
for  practically  all  pictorial  work. 

The  first  rule  in  oblique  drawing  is:  Place  the  object  so  that 
the  irregular  ouiline  or  contour  faces  the  front. 

If  there  is  no  irregular  outline  the  second  rule  should  be  fol- 
lowed: Always  place  the  object  so  that  the  longest  dimension 
shows  in  the  front. 


48 


MECHANICAL  DRAWING 


43.  Circles. — On  the  front  face  circles  and  curves  show  in 
their  true  shape.     On  the  other  faces  they  are  drawn  as  in 
isometric,  by  drawing  perpendicular  lines  from  the  tangent  points. 

44.  Making  an  Oblique  Drawing. — Problem:  Make  an  oblique 
drawing  of  the  bearing,  Fig.  101.     First,  draw  the  axes  for-  the 


FIG.  101. — Problem  for  oblique  drawing. 

base,  AB,  AC,  and  AD,  in  second  position,  and  measure  on  them 
the  length,  width  and  thickness  of  the  base,  Fig.  102,  A.  Draw 
the  base  and  on  it  block  in  the  upright  omitting  the  projecting 


B  c 

FIG.  102. — Stages'in  oblique  construction. 

boss,  as  shown  in  the  figure.  Second,  block  in  the  boss,  as  at  B 
and  find  the  centers  for  all  circles  and  arcs.  Third,  draw  the 
circles  and  circle  arcs.  Fourth,  finish  the  drawing  as  at  C. 

45.  Cabinet  Drawing.— In  this  form  of  drawing  the  axes  are 
taken  the  same  as  in  oblique  drawing  but  all  measurements 
parallel  to  the  oblique  or  cross  axis,  or  in  other  words  all  thickness 
measurements  from  front  to  back,  are  reduced  one-half.  It  is 
used  sometimes  in  making  drawings  of  wood  construction. 


THEORY  OF  SHAPE  DESCRIPTION 


49 


46.  Perspective  Drawing. — Perspective  drawing  is  the  repre- 
sentation of  an  object  as  it  actually  appears  to  the  eye.  A  sketch 
made  in  perspective  thus  gives  the  best  pictorial  effect.  The 
elementary  principles  of  perspective  are  familiar  .to  most  students 


FIG.   103. — Angular   perspective. 


'  '  *  •  c 

.x 

I 

'/ 

FIG.   104. — Parallel  pei^pective. 

through  the  study  of  freehand  drawing  and  they  will  find  this 
knowledge  of  value  in  studying  shape  description.1 

1  In  the  scope  of  this  book  the  interesting  subject  of  mechanical  perspective 
construction  cannot  be  taken  up.  With  a  knowledge  of  its  methods  per- 
spective drawings  can  be  made  from  working  drawings,  as  for  example 
when  an  architect  makes  a  picture  of  a  proposed  building,  the  result  being  as 
accurate  as  a  photograph  of  the  building. 
4 


50 


MECHANICAL  DRAWING 


In  the  perspective  sketch,  Fig.  103,  it  will  be  noted  that  the 
vertical  lines  remain  vertical  and  that  the  two  sets  of  horizontal 
lines  each  converge  toward  a  point  called  the  vanishing  point. 
These  two  vanishing  points  lie  on  a  horizontal  line  at  the  level 
of  the  eye  called  the  horizon.  The  first  rule  is,  all  horizontal 
lines  vanish  on  the  horizon. 

When  the  object  is  turned  at  an  angle  as  in  Fig.  103,  the  draw- 
ing is  said  to  be  in  angular  or  "two  point"  perspective. 

If  the  object  is  turned  so  that  one  face  is  parallel  to  the  front 
plane,  the  horizontal  lines  on  that  face,  or  parallel  to  it,  remain 

horizontal  and  have  no  vanishing 
point.  This  drawing  is  called  paral- 
lel or  "one  point"  perspective, 
Fig.  104. 

47.  Making  a  Perspective 
Sketch. — In  sketching  from  the 
object,  place  it  below  the  level  of 
the  eye  (unless  very  large)  and  so 
as  to  show  the  outline  of  shape  to 
the  best  advantage.  Start  by 
drawing  a  line  for  the  nearest 
vertical  corner.  From  this  sketch 
lightly  the  directions  of  the  prin- 
cipal lines,  running  them  past  the 
limits  of  the  figure.  Test  the  di- 
rections and  proportionate  lengths 
with  the  pencil  as  follows:  With 
the  drawing  board  or  sketch  pad  held  perpendicular  to  the  "line  of 
sight  "from  the  eye  to  the  object,  hold  the  pencil  at  arm's  length 
paralklto  the  board  and  rotate  the  arm  until  the  pencil  appears  to 
coincide  with  the  line  on  the  model,  then  move  it  parallel  to  this 
position  back  to  the  board.  This  gives  the  direction  of  the  line. 
To  estimate  the  apparent  lengths  hold  the  pencil  the  same  way 
and  mark  with  the  thumb,  Fig.  105,  the  length  of  the  pencil 
which  covers  the  line.  Rotate  the  arm  with  the  thumb  held  in 
position  until  the  pencil  coincides  with  another  line  and  estimate 
the  proportion  of  this  measurement  to  the  second  line. 

Block  in  the  enclosing  squares  for  all  circles  and  circle  arcs 
and  carry  on  the  figure.  Work  with  light  free  sketchy  lines 
and  do  not  erase  any  lines  until  the  whole  sketch  is  blocked  in. 
Draw  main  outlines  first,  then  add  details.  Finally,  brighten 
the  sketch  with  heavier  lines. 


FIG.  105. — Estimating  proportions. 


CHAPTER  IV 
PRINCIPLES  OF  SIZE  DESCRIPTION 

48.  We  have  learned  that  the  two  things  to  be  told  about  an 
object  are  its  shape  and  its  size.  In  the  previous  chapter  we 
studied  the  methods  of  representing  the  shape.  When  informa- 
tion regarding  the  size  is  added  to  the  shape  description,  the  two 
together  give  the  complete  working  drawing  of  the  object. 

While  working  drawings  are  always  made  to  scale,  it  would 
require  too  much  time  to  take  off  distances  by  applying  a  scale 
to  the  drawing.  Furthermore,  the  chances  of  making  a  mistake 
would  be  numerous  especially  with  small  distances  or  for  draw- 
ings made  to  small  scale. 

For  convenience  in  using,  insuring  accuracy,  and  saving  time, 
the  size  description  is  given  in  the  form  of  dimensions  and  notes, 
arranged  on  the  drawing  in  a  definite  manner. 


4- 


Dimension  line 


Extension  //ne 


FIG.  106. — Dimension   lines. 

49.  Lines,  Figures,  Arrows,  Etc. — Certain  conventional  lines 
and  symbols  are  used  and  the  draftsman  to  make  a  successful 
drawing  must  not  only  be  familiar  with  these  but  must  know  the 
principles  of  dimensioning  and  be  acquainted  with  the  shop 
processes  which  will  be  used  in  building  or  making  the  object 
represented. 

51 


52  MECHANICAL  DRAWING 

The  dimension  line  is  made  a  light  full  line,  in  contrast  with 
the  heavier  shape  outline.  See  Alphabet  of  Lines,  Art.  62.  The 
line  is  terminated  by  long  pointed  arrow-heads,  Fig.  106.  Great 
care  must  be  taken  to  have  all  arrow-heads  the  same  size,  and 
correctly  shaped,  Fig.  107. 

A  space  is  left  in  the  dimension  line  for  a  figure  to  tell  the 
actual  distance  on  the  full-size  piece.  When  the  dimension  is 
placed  outside  of  the  outline  of  the  view 


I Nrtthus     extension  or  witness  lines  are  drawn  from  the 

-  Not  thus     view  to  show  the  points  or  surfaces  measured 
on  the  object.     Extension  lines  are  fine  lines 
drawn  from  the  outline  and  extending  past 
the  arrow-head.      Since  extension  lines  are  not   part   of  the 
shape  they  should  not  touch  the  outline,  see  Fig.  106. 

Figures  must  be  carefully  made  and  of  a  size  easily  readable 
but  not  so  large  as  to  overbalance  the  drawing.  In  general 
make  them  about  %"  high.  To  avoid  crowding,  extension 
lines  should  be  KG"  or  more  from  the  lines  of  the  drawing  and 
from  each  other.  A  fraction  is  always  made  with  a  horizontal 
division  line.  Figures  for  fractions  are  made  about  two-thirds 
the  height  of  whole  numbers,  see  Fig.  24. 

50.  Placing  Dimensions. — In  placing  dimensions  the  impor- 
tant thought  is  for  the  man  who  has  to  read  the  drawing  and  make 
the  piece  from  it.  It  is  necessary  to  think  of  the  actual  piece  in 
space.  Since  the  shape  is  already  defined,  select  the  view  which 
tells  most  about  the  piece  and  give  two  dimensions  of  each  part. 
One  of  the  other  views  must  be  used  to  tell  the  third  distance. 
In  general  it  is  better  to  place  the  dimensions  between  the  views 
so  as  to  be  near  both  views.  Horizontal  dimensions  must  always 
read  from  the  bottom  of  the  sheet  and  vertical  dimensions  from 
the  right  side  of  the  sheet,  no  matter  what  part  of  the  sheet  they 
are  on. 

Inches  are  indicated  by  (")  and  feet  by  (')  and  a  dash  is  always 
placed  between  feet  and  inches  thus,  5'-7J",  or  0'-9J". 
When  the  drawing  is  dimensioned  entirely  in  inches,  the  inch 
marks  may  be  omitted.  When  the  space  is  too  small  to  admit 
of  arrow-heads  and  figures,  one  of  the  methods  of  Fig.  108  is 
used. 

When  there  are  few  lines  within  the  outline,  dimensions  may 
be  placed  inside,  making  it  unnecessary  to  draw  extension  lines. 


PRINCIPLES  OF  SIZE  DESCRIPTION 


53 


Dimension   lines   should   never   cross   extension   lines.     Larger 
dimensions  should  be  placed  outside  of  smaller  dimensions. 
51.  Theory  of  Dimensioning. — The  theory   of   dimensioning 


FIG.  108. — Dimensioning  in  limited  space. 
i 

is  based  upon  the  idea  of  considering  any  object  as  made  up  of 
a  number  of  simple  shapes.  When  the  size  of  each  simple  piece 
is  defined  and  the  relative  posi- 
tions given,  the  size  description 
is  complete.  When  a  number 
of  pieces  are  assembled,  each 
piece  is  first  considered  separately 
and  then  in  relation  to  the  other 
pieces.  In  this  way  the  size  de- 
scription of  a  complete  machine, 

of  a  piece  of  furniture  or  of  a  building  %s  no  more  difficult  than 
the  dimensioning  of  a  single  piece. 


r 


1 


*r''-i' 
»_ 


FIG.  110. — First  rule  applied. 


FIG.  111. — First  rule  applied. 


52.  The  first  shape  is  a  flat  piece,  requiring  the  length,  breadth 
and  thickness,  Fig.  109.  Such  an  elementary  shape  may  appear  in 
a  great  many  ways,  a  few  of  which  are  shown  in  Figs.  110  and  111. 


54 


MECHANICAL  DRAWING 


Flat  pieces  of  irregular  shape  are  dimensioned  in  a  similar  way, 
Figs.  112  and  113. 

Rule. — For  any  flat  part  give  the  thickness  in  one  of  the  edge  views 
and  all  other  dimensions  on  the  outline  view. 


FIG.   112. — An  irregular  flat  shape. 


FIG.  113. — An  irregular  flat  shape. 


FIG.  114. — The  second  shape. 


FIG.   115. — Second  rule  applied. 


The  second  shape  is  the  cylinder,  requiring  two  dimensions, 
the  diameter  and  length,  Fig.  114.  'A  washer  may  be  thought  of 
as  two  cylinders,  Fig.  115,  requiring  two  diameters  and  one 
length. 


PRINCIPLES  OF  SIZE  DESCRIPTION 


55 


Rule. — For  cylindrical  pieces  give  the  diameter  and  length  on  the 
same  view. 

Combinations  of  the  first  and  second  shapes  are  shown  in  Figs. 
116  and  117.     The  dimensions  A,  B, 
C  and  D,  Fig.  117,  establish  the  rela- 
tion between  the  single  shapes. 

53.  General  Rules. — In  the  appli- 
cation of  dimensioning  there  are  cer- 
tain  practices  which  have   come  to 
represent  good  form  to  such  an  extent 
as  to  have  the  force  of  rules. 

1.  Regardless  of  location  on  the  sheet, 
dimensions    must    read    in    line   with   the 
dimension  line  and  either  from  the  lower  or 
right-hand  side  of  the  sheet. 

2.  On  machine  drawings  detail  dimen- 
sions up  to  24"  should  be  given  in  inches. 

Above   this   feet  and  inches  are  generally     ^  116_First  and  second 
used,  except  for  gear  drawings,  bore  of  cyhn-  shapes, 

ders,  length  of  wheel  bases,  etc. 


FIG.   117. — First  and  second  shapes. 

3.  On  architectural  and  structural  drawings,  dimensions  of  12"  and  ovei 
are  given  in  feet  and  inches. 

4.  Sheet  metal  drawings  are  usually  dimensioned  entirely  in  niches. 

5.  Furniture  and  cabinet  drawings  are  usually  dimensioned  in  inches. 

6.  Feet  and  inches  are  designated  thus,  7'-3",  or  7  ft.-3  in.     Where  the 
dimension  is  in  even  feet  it  is  indicated  thus,  7'-Q". 


56 


MECHANICAL  DRAWING 


7.  The  same  dimension  is  not  repeated  on  different  views  unless  there  is  a 
special  reason  for  it. 

8.  When  it  is  necessary  to  place  a  dimension  within  a  sectioned  area  do 
not  run  the  section  lines  across  the  number,  Fig.  118. 

9.  Dimensions  should  be  given  from 
or  about  center  lines.  Finished  surfaces 
are  always  located  from  other  finished 
surfaces  or  from  center  lines. 

10.  Never    use    a    center   line   as   a 
dimension  line. 

11.  Never  use  a  line  of  the  drawing  as 
a  dimension  line. 

12.  Never   have   a  dimension  line  a 
continuation  of  a  line  of  the  drawing. 

13.  Never  place  a  dimension  so  that 
it  is  crossed  by  a  line. 

14.  Always   give   the   diameter    of   a 
circle,  not  the  radius. 

15.  Always  give  the  radius  of  an  arc.     The  abbreviation  R  or  Rad.  is 
used  when  necessary,  Fig.  108. 

54.  Use  of  Decimals. — Dimensions  are  given  in  feet,  inches 
and  fractions  of  an  inch.     In  ordinary  work  binary  fractions 


FIG.  118. 


L 


a  -Spot  for  sef  screw 


FIG.  119.  —  Dimensioning  with  limits. 


such  as  Yz",  K",  H",  Ke",  M2",  Hi"  are  used.  For  parts 
which  must  fit  very  accurately  the  dimensions  are  given  in  deci- 
mals instead  of  the  usual  fractions,  and  the  workman  is  required 
to  work  within  a  certain  fixed  limit  of  accuracy.  The  number 


PRINCIPLES  OF  SIZE  DESCRIPTION  57 

of  thousandths  or1"  ten-thousandths  of  an  inch  which  will  be 
allowed  as  variance  from  the  absolute  measurement  is  called  the 
tolerance.  The  limits  between  which  the  measurement  must 
come  are  given  as  in  Fig.  119,  which  shows  that  the  diameter  of 
the  hole  must  not  be  over  .8130"  nor  under  .8125". 

55.  Dimensioning  Assembled  Parts. — The  drawing  of  a  sepa- 
rate part  is  called  a  detail  drawing.     When  the  different  parts  of 
a  machine  or  structure  are  shown  together  in  their  relative  posi- 
tions the  drawing  is  called  an  assembly  drawing.     The  rules  and 
methods  given  for  dimensioning  apply  to  all  cases  where  a  com- 
plete description  of  size  is  required. 

Drawings  of  complete  machines,  pieces  of  furniture,  etc.,  are 
made  for  different  uses  and  have  to  be  dimensioned  to  serve  the 
purpose  desired  of  them.  If  the  drawing  is  simply  to  show  the 
arrangement  of  parts  all  dimensions  are  left  off.  When  it  is 
desired  to  tell  the  space  required,  give  "over-all"  dimensions. 
Where  it  is  necessary  to  locate  parts  in  relation  to  each  other 
without  giving  all  of  the  detail  dimensions,  it  is  usual  to  give 
center  distances  and  size  of  parts  which  might  affect  putting 
together  the  machine  or  construction.  Assembly  drawings  may 
be  completelv  dimensioned,  either  with  or  without  extra  part 
views,  see  Fig.  163.  Such  drawings  serve  the  purpose  of  both 
detail  and  assembly  drawings. 

For  furniture  and  cabinet  work  the  major  dimensions  only  are 
sometimes  given,  such  as  length,  breadth,  height,  and  sizes  of 
stock,  leaving  the  details  of  joints  to  the  cabinetmaker.  This  is 
common  practice  where  machinery  is  used  and  where  many 
details  of  construction  are  standardized. 

56.  Sketching  and  Measuring. — Sketching  as  a  means  of  shape 
description  and  study  has  been  considered  in  Chapter  III.     When 
sketches  are  made  from  machine  or  furniture  parts,  to  be  used 
in  making  drawings  it  is  necessary  to  define  the  size,  the  material, 
the  kinds  of  surfaces,  either  " finished"  or  "rough,"  the  limits 
of  accuracy  and  all  information  that  might  have  any  possible 
future  value. 

57.  After  sketching  the  views  of  a  piece,  add  all  necessary 
dimension  lines  in  exactly  the  same  way  as  for  a  drawing.     The 
piece  should  now  be  examined,  the  kind  of  material  noted,  to- 
gether with  the  kinds  of  finish  and  the  location  of  all  finished 
surfaces.     When  everything  else  is  done  it  is  time  to  measure 
the  piece  and  fill  in  the  figures,  telling  the  size.     For  this  purpose 


58 


MECHANICAL  DRAWING 


various  measuring  tools  will  be  required.  A  two-foot  rule,  a 
steel  scale  and  a  pair  of  calipers  will  be  found  sufficient  for  most 
measurements.  Other  machinists'  tools  are  often  necessary  or 
convenient  and  the  pupil  should  know  something  about  the  tools 
which  are  available  and  how  to  use  them. 


FIG.  120. — Taking  a  measurement. 

58.  The  flat  scale  or  the  steel  scale  and  straightedge  can  be 
used  in  many  ways,  as  suggested  in  Fig.  120  and  the  distances 
read  directly. 


FIG.   121. — Outside  and  inside  calipers. 

Whenever  possible,  always  take  measurements  from  finished 
surfaces.  Inside  and  outside  calipers  with  their  use  illustrated 
are  shown  in  Fig.  121.  The  distance  between  the  contact  points 
is  read  by  applying  the  calipers  to  a  scale,  Fig.  122. 


PRINCIPLES  OF  SIZE  DESCRIPTION 


59 


When  the  calipers  cannot  be  removed  from  a  thickness,  the 
plain  calipers  may  be  used  by  inserting  an  extra  piece  or  "filler" 
Fig.  123;  or  the  " transfer"  calipers,  Fig.  124,  may  be  used.  The 
distance  x  must  be  subtracted  from  the  total  distance  to  obtain 


FIG.  122. — Reading  the  calipers. 

the  desired  thickness  t  when  a  filler  is  used.  The  transfer  calipers 
are  provided  with  a  false  leg  which  is  set  so  that  the  calipers  may 
be  opened  and  then  brought  back  to  the  same  position  after 
removing  from  the  casting. 


FIG.   123.— Use   of   filler. 


FIG.  124. — Use  of  transfer  calipers. 


All  measurements  of  wood  construction  can  generally  be  ob- 
tained with  sufficient  accuracy  by  using  the  two-foot  rule. 

For  very  accurate  measurements  vernier  calipers  and  microme- 
ter calipers,  Figs.  125  and  126  are  used.  Other  tools  which 
are  useful  if  at  hand  are  the  steel  square,  try  square,  combination 
square,  surface  gauge,  depth  gauge,  radius  gauges,  protractor, 
etc. 

When  a  pictorial  sketch  is  dimensioned  the  only  additional 
consideration  is  to  use  care  to  see  that  all  extension  lines  are 


60 


MECHANICAL  DRAWING 


either  in  or  perpendicular  to  the  plane  on  which  the  distance  is 
being  given,  Fig.  127. 


3  4 

AS6789|12345676?   I  123456769 
lllinillllllllHIIIIIIIIIIIttllllllllll 


FIG.  125. — Vernier  calipers. 

59.  Notes  and  Specifications. — Information  which  cannot  be 
represented  graphically  must  be  given  in  the  form  of  lettered 


A-  Frame 
B- Anvil 
C-Sp/nd/e 
D-Sleere 
-  Th/'mb/e 


FIG.  126. — Micrometer  calipers. 

notes  and  symbols.     Generally  understood  trade  information 
is  often  given  in  this  way.     Such  notes  include  the  following 


FIG.  127. — Dimensioning  a  pictorial  sketch. 

items:  Number  required,  material,  kind  of  finish,  kind  of  fit, 
method  of  machining,  kinds  of  screw  threads,  kinds  of  bolts 
and  nuts,  sizes  of  wire,  thickness  of  sheet  metal,  etc. 

The  materials  in  most  general  use  are  wood,  cast  iron,  wrought 


PRINCIPLES  OF  SIZE  DESCRIPTION  61 

iron,  steel  and  brass.  All  parts  which  go  together  must  be  of  the 
proper  size  so  they  will  fit.  Some  pieces  are  left  in  the  rough 
and  others  must  have  a  smooth  " finish."  The  wood  used  for 
making  a  piece  of  furniture  is  first  shaped  with  wood-working 
tools.  Cast  iron  and  brass  are  given  the  required  form  by  mould- 
ing, casting,  and  machining.  First  a  wooden  " pattern"  of  the 
shape  and  size  required  is  made.  This  pattern  is  placed  in  sand 
to  make  an  impression  or  mould,  into  which  the  melted  metal  is 
poured.  Wrought  iron  and  steel  are  made  into  shapes  by  rolling 
or  forging  in  the  rolling  mill  or  blacksmith  shop.  Some  kinds  of 
steel  may  be  cast  as  described  for  cast  iron. 

There  are  many  interesting  ways  of  forming  metals  for  special 
purposes,  and  many  special  alloys,  that  cannot  be  described  in  a 
drawing  book,  but  the  pupil  will  learn  much  by  observing  the 
shapes  of  parts  of  machinery  and  the  materials  of  which  they  are 
made. 

After  a  part  is  cast  or  forged  it  must  be  "machined"  on  all 
surfaces  which  are  to  fit  other  surfaces.  Round  surfaces  are 
generally  formed  on  a  lathe.  Flat  surfaces  are  finished  or 
smoothed  on  a  planer,  milling  machine,  or  shaper.  For  making 
holes  drill  presses,  boring  mills  or  lathes,  are  used. 

Extra  metal  is  allowed  for  surfaces  which  are  to  be  finished. 
To  specify  such  surfaces  a  small  "f"  is  placed  on  the  lines  which 
represent  the  surfaces.  If  the  entire  piece  is  to  be  finished  a 
note  such  as  "fin.  all  over"  may  be  used  and  all  other  marks 
omitted. 

Specifications  as  to  methods  of  machining,  finish  and  other 
treatment  are  given  in  the  form  of  notes,  as  spot  face,  grind, 
polish,  knurl,  core,  drill,  ream,  countersink,  hardened,  case- 
hardened,  blued,  and  tempered. 

It  is  often  necessary  to  add  notes  in  regard  to  assembling, 
order  of  doing  work  or  other  special  directions. 

60.  Checking  a  Drawing. — After  a  drawing  has  been  completed 
it  must  be  very  carefully  examined  before  it  is  used.  This  is 
called  checking  the  drawing.  It  is  very  important  work,  and 
should  be  done  by  someone  who  has  not  worked  on  the  drawing. 

Thorough  checking  requires  a  definite  order  of  procedure,  and 
consideration  of  the  following  items: 

1.  See  if  the  views  completely  describe  the  shape  of  each  piece. 

2.  See  if  there  are  any  unnecessary  views. 

3.  See  that  the  scale  is  sufficiently  large  to  show  all  detail  clearly. 


62 


MECHANICAL  DRAWING 


FIG.   128. — An  incorrect  drawing.     To  be  redrawn. 


FIG.  129. — The  drawing  corrected. 


PRINCIPLES  OF  SIZE  DESCRIPTION  63 

4.  See  that  all  views  are  to  scale  and  that  correct  dimensions  are  given. 

5.  See  that  sufficient  dimensions  are  given  to  define  the  size  of  all  parts 
completely. 

6.  See  that  the  kind  of  material  and  the  number  required,  of  each  part  is 
specified. 

7.  See  that  the  kind  of  finish  is  specified,  that  all  finished  surfaces  are 
marked  and  that  finish  is  not  called  for  where  not  heeded. 

8.  See  that  all  necessary  explanatory  notes  are  given,  and  that  they  are 
properly  placed. 

An  incorrect  drawing  with  some  of  the  mistakes  noted  on  it 
is  shown  in  Fig.  128,  and  the  same  drawing  when  corrected  in 
Fig.  129. 


CHAPTER  V 
TECHNIC  OF  THE  FINISHED  DRAWING 

61.  We  have  had  it  impressed  upon  us  that  in  the  language  of 
drawing  an  object  is  described  by  telling  its  shape  and  its  size. 
All  drawings  whether  for  machinery,  structural  work,  buildings 
or  ships  are  made  on  the  same  principles. 

Sometimes  an  unfavorable  comparison  is  made  between  a 
student's  drawing  and  a  real  drawing.  The  finished  appearance 
of  a  real  drawing  as  made  by  a  draftsman  or  engineer  is  due  to  a 
thorough  knowledge  of  the  technic  of  commercial  drafting.  The 
correct  order  of  going  about  the  work  and  some  of  the  conven- 
tional representations  in  common  use  are  described  in  this  chapter. 
The  pupil  must  become  thoroughly  familiar  with  this  practice 
if  his  drawings  are  to  have  the  style  and  good  form  which  are 
so  desirable  and  necessary. 

62.  Alphabet  of  Lines. — The  kinds  of  lines  in  general  use  in 


•    (1)   Visible  outline. 

(2)  Invisible  outline. 

(3)  Center  line. 

9X/ 
' 2 of — =*-J    (4)   Dimension  line. 

'• (5)   Extension  line. 

(6)  Cutting  plane. 

(7)  Limiting  break. 

(8)  Broken  parts. 


.  Fia.   130.— The  alphabet  of  lines. 

making  drawings  are  given  in  Fig.  130.  Each  line  is  used  for  a 
definite  purpose  and  must  not  -be  used  for  anything  else.  Detail  • 
drawings  should  have  fairly  heavy  outlines,  with  light  center 
lines  and  dimension  lines  so  that  the  drawing  will  have  contrast 
and  be  easy  to  read.  If  all  the  lines  are  the  same  weight  the 
drawing  will  have  a  flat  appearance  making  it  hard  to  read. 

64 


TECHNIC  OF  THE  FINISHED  DRAWING  65 

63.  Order  of  Penciling. — After  learning  about  shape  and  size 
description  the  most  important  thing  for  the  young  draftsman 
to  get  is  good  form,  a  systematic  method  of  working.     The  order 
of  making  the  different  parts  of  the  drawing  is  the  first  item.     A 
drawing  is  started  by  drawing  center  lines  and  base  lines,  which 
form  the  skeleton  for  the  views.     The  views  should  be  carried 
along  together.     Do  not  attempt  to  finish  one  view  before  making 
another.     Learn  the  following  order  of  penciling  and  follow  it  as 
nearly  as  possible  in  every  drawing. 

1.  Lay  off  the  sheet  to  proper  size,  and  block  in  the  title  space  or  record 
strip. 

2.  Plan  the  arrangement  of  views. 

3.  Draw  the  primary  center  and  base  lines. 

4.  Lay  off  the  principal  measurements. 

5.  Block  in  the  views  by  drawing  the  preliminary  and  final  "blocking- 
in"  lines. 

6.  Lay  off  the  detail  measurements. 

7.  Draw  the  center  lines  for  details.     See  that  two  intersecting  center 
lines  are  drawn  to  locate  all  circles,  and  that  there  are  center  lines  for  the 
axes  of  all  cylinders. 

8.  Draw  all  complete  circles  and  the  preliminary  and  final  lines  for 
details. 

9.  Draw  part  circles,  fillets  and  rounded  corners. 

10.  Draw  such  lines  as  could  not  be  previously  drawn. 

11.  Draw  all  extension  and  dimension  lines. 

12.  Put  on  dimensions  and  notes. 

13.  Cross-hatch  all  sectioned  surfaces. 

14.  Put  on  title. 

15.  Check  drawing. 

64.  Inking  and  Tracing. — Finished    drawings    are  generally 
inked,  either  by  going  over  the  pencil  lines  with  drawing  ink  or 
more  commonly  by  putting  a  piece  of  tracing  cloth  or  paper  over 
the  pencil  drawing  and  tracing  it  in  ink.     From  such  tracings 
blueprints  can  be  made  for  use  on  the  work.     The  method  of 
procedure  is  the  same  for  paper  or  cloth. 

All  straight  lines  are  inked  with  the  ruling  pen.  Hold  the  pen 
point  downward  and  fill  by  touching  the  quill  on  the  ink  bottle 
cork  to  the  inside  of  the  pen  blades.  The  nibs  of  the  pen  are 
set  to  the  desired  width  of  line  by  turning  the  adjusting  screw, 
using  the  thumb  and  second  finger  of  the  pen  hand.  Then 
hold  the  pen  against  the  T-square  or  triangle  in  the  position  of 
Fig.  131. 


66 


MECHANICAL  DRAWING 


Note  the  following: 

Do  not  hold  the  pen  over  the  drawing  while  filling. 

Keep  the  blades  parallel  to  the  direction  of  the  line. 


FIG.  131.  —  Correct  position  of  pen. 

Do  not  press  too  hard  against  the  T-square. 
Do  not  screw  the  nibs  of  the  pen  too  tight. 
Have  a  pen  wiper  at  hand. 


Pen  pressed  aga/nsf  T  square 


Per?  s/oped  away  from  Tsqvare 


Pen  foo  c/ose  fo  edge  /nk  ran  under 


fnk  on  oufs/de  of  b/ade,  ran  under 


Pen  b/ades  r?of  kepf  para//e/  fo  Tsauare 


Tsqyare(orfr/ang/eJ  s/ipped  into  wef//ne 

Not  enough  ink  fo  finish  //ne 

FIG.  132. — Faulty  lines. 

Keep  the  pen  clean.     Always  wipe  it  out  carefully  after  using. 
Never  dip  the  pen  into  the  ink  bottle  or  allow  ink  to  get  on  the  outside  of 
the  blades. 

Do  not  put  too  much  ink  in  the  pen.     (Not  over  Y±  inch.) 


TECHNIC  OF  THE  FINISHED  DRAWING 


67 


Faulty  lines  occur  from  different  reasons.  The  pen  may  need 
dressing  or  sharpening.  The  beginner  should  not  attempt  to 
do  this  but  should  ask  the  teacher  to  do  it  for  him.  Figure  132 
shows  some  of  the  common  faults  and  suggests  the  remedy. 

The  irregular  curve,  Fig.  14,  is  used  for  guiding  the  pen  when 
inking  curves  other  than  circle  arcs.  It  is  used  by  matching  a 
portion  of  the  curved  line  and  drawing  a  piece  of  the  line,  then 
moving  the  curve  to  a  new  position.  The  new  position  must 
always  match  a  part  of  the  line  already  inked. 

For  inking  circles  the  compasses  and  bow  pen  are  used.  Re- 
move the  pencil  leg  from  the  compasses  and  insert  the  pen  leg,  ad- 
justing the  needle  point  until  it  is  very  slightly  longer  than  the  pen. 


FIG.  133. — Inking  a  circle. 

The  joints  of  the  compasses  should  be  adjusted  so  that  the  legs 
are  perpendicular  to  the  paper.  Always  draw  a  circle  in  one 
stroke,  inclining  the  compasses  in  the  direction  of  the  line  and 
rolling  the  handle  between  the  thumb  and  finger,  Fig.  133. 
Small  circles  are  drawn  with  the  bow  compasses. 

65.  To  Make  a  Tracing. — First  tear  off  the  selvage  and  tack 
the  cloth  down  smoothly  over  the  pencil  drawing.  Most  drafts- 
men place  the  dull  side  up.  Dust  the  surface  with  chalk  and 
rub  over  with  a  cloth  to  remove  all  traces  of  grease  so  as  to 
obtain  smooth  ink  lines.  Be  sure  to  remove  all  dust  before 
starting  to  ink.  With  the  tracing  cloth  in  position  and  properly 
prepared  inking  is  done  in  exactly  the  same  way  as  on  paper. 


MECHANICAL  DRAWING 


As  tracing  cloth  is  very  sensitive  to  atmospheric  changes  and 
will  stretch  if  left  over  night,  no  view  should  be  started  which 
cannot  be  finished  on  the  same  day.  When  work  is  again  started 
the  cloth  should  be  restretched. 

66.  Order  of  Inking. — Good  inking  is  the  result  of  two  things, 
careful  practice  and  a  definite  order  of  working.     Smooth  joints 
and  tangents,  sharp  corners  and  neat  fillets  not  only  improve 
the  appearance  of  a  drawing  but  make  it  easier  to  read. 

1.  Ink  center  lines. 

2.  Ink  small  circles  and  arcs. 

3.  Ink  larger  circles  and  arcs. 

4.  Ink  irregular  curves. 

5.  Ink  horizontal  full  lines. 

6.  Ink  vertical  full  lines. 

7.  Ink  inclined  full  lines. 

8.  Ink  dotted  circles  and  arcs. 

9.  Ink  dotted  lines. 

10.  Ink  extension  and  dimension  lines. 

11.  Ink  arrow-heads  and  figures. 

12.  Ink  section  lines. 

13.  Letter  notes  and  title. 

14.  Ink  border  lines. 

15.  Check  drawing. 

67.  Erasing. — The  ideal  way  of  course  is  to  complete  a  drawing 
or  tracing  without  having  to  do  any  erasing.     Sometimes,  how- 
ever, it  is  necessary  to  make  an  erasure  on  account  of  a  change 
or  a  mistake.     Ink  lines  may  be  removed  by  rubbing  rather  hard 
with  a  pencil  eraser,  which  does  not  abrade  the  surface  of  the 
paper  or  cloth  as  does  an  ink  eraser.     Do  not  use  a  knife  or 
scratcher.     An  erasing  shield  is  very  convenient.     One  can  be 
made  by  cutting  a  slot  in  a  card  or  piece  of  drawing   paper. 
Pencil  lines  are  removed  with  artgum  or  a  pencil  eraser. 


fix*  Number 

Number  Req. 

Material 

THE 

SEAC 

IRAVE 

CO.,  C 

JOLUNI 

BUS,  OHIO 

DATE 

DRAWER 

FIG.  134.— A  boxed  title  form. 

68.  Titles. — Every  sketch  and  drawing  must  have  some  kind 
of  title,     The  form,  completeness  and  location  vary.     On  work- 


TECHNIC  OF  THE  FINISHED  DRAWING  69 

ing  drawings  the  title  is  usually  " boxed"  in  the  lower  right-hand 
corner,  Fig.  134,  or  as  part  of  a  record  strip  extending  across  the 
bottom  or  end  of  the  sheet,  Fig.  135. 

The  title  gives  as  much  as  is  necessary  of  the  following  in- 
formation : 

1.  The  name  of  the  construction. 

2.  The  name  of  the  part  shown  (or  simply  "details"). 

3.  Manufacturer;  company  or  firm  name  and  address. 

4.  Date;  usually  date  of  completion  of  tracing. 

5.  Scale,  or  scales. 

6.  Drafting-room  record;  names  or  initials  of  draftsman,  tracer,  checker, 
and  approval  of  chief  draftsman,  engineer  or  superintendent. 

7.  Numbers,  of  the  drawing;  of  the  order. 

In  larger  drafting  rooms  the  title  is  often  printed  in  blank 
on  the  paper  or  cloth  used. 


UNIT 

HAUC  0»  MCCC 

•KMT. 

""  MlST^WMMC 

DM. 

•AT. 

race  »•- 

THE  LODGE  4.  SHIPLEY  MACHINE  TOOL  Co. 

CINCINNATI.  OHIO.  U.   «.  A. 

FIG.  135. — A  record  strip  title. 

69.  Bill  of  Material. — Drawings  may  have  the  name  of  the 
part,  material,  number  required,  •  part  number,  etc.,  given  in  a 
note  near  the  views  of  each  part.     Another  method  often  used 
is  to  place  the  number  of  the  part  in  a  circle  near  the  views  and 
then  collect  all  the  information  in  a  tabulated  list,  called  a  bill 
of  material,  or  material  list.     Sometimes  this  list  is  placed  on  the 
drawing  over  the  title,  and  sometimes  it  is  typewritten  on  a 
separate  sheet.     If  for  wood  construction   the   bill    will    give 
the  stock  sizes,  kind  and  quality  of  wood,  board  measure,  and 
number  of  each  part  required,  Fig.  136.     Sometimes  the  cost  is 
added.     Bolts  and  other  metal  parts  are  often  specified  and 
marked  with  an  identification  number  or  mark. 

70.  Screw  Threads.— The  use  of  screw  threads  is  so  frequent 
that  the  common  forms  and  methods  of  representation  must  be 
understood.     The  most  familiar  occurrence  of  screw  threads  is 
on  the  ordinary  wood  screw,  and  common  bolt,  Figs.  137  and 
138. 


70 


MECHANICAL  DRAWING 


The  form  of  thread  generally  used  in  this  country  for  machine 
bolts  and  metal  constructions  is  the  United  States  Standard, 
shown  in  Fig.  139.  Wood  screw  threads  have  a  space  between 
them  to  allow  for  the  difference  in  strength  of  wood  and  metal. 


\DEScximoN 


Gauge  X  -3  -J 


BOX  FOR 
OVERSEAS  SHIPMENT 


FIG.  136. — Drawing  with  bill  of  material. 

Other  forms  of  threads  used  'to  meet  various  requirements  are 
illustrated  and  named  in  the  figure. 

To  draw  a  true  representation  of  a  screw  thread  it  is  necessary  to 
draw  the  projection  of  a  cylindrical  helix.     A  cylindrical  helix 


Round  head 


Slot, 


Diameter  *(  ^  Pitch 


Flat-  head 
FIG.  137. — Wood  screws. 


=J/        ^  Root  diameter 

Head  h — Length        H 

FIG.   138. — Hex  head  bolt  and  nut. 


is  a  curve  generated  by  a  point  moving  uniformly  around  a  cylin- 
der and  uniformly  lengthwise  of  the  cylinder  at  the  same  time. 
The  hypotenuse  of  a  right  triangle  will  form  one  turn  of  a  helix 
if  it  is  wrapped  around  a  cylinder,  as  in  Fig.  140.  The  base  of 


TECHNIC  OF  THE  FINISHED  DRAWING 


71 


the  triangle  is  equal  to  the  circumference  of  the  cylinder  and  the 
altitude  is  the  pitch  of  the  helix. 

71.  To  Draw  the  Projection  of  a  Helix. — Draw  two  projec- 
tions of  the  cylinder,  divide  the  top  view  into  a  number  of  equal 
parts  and  the  pitch  into  the  same 
number  of  parts  as  at  A,  Fig.  141. 
From  each  point  in  the  top  view  drop 
perpendiculars  to  meet  horizontal 
lines  drawn  through  the  same  num- 
bered division  of  the  front  view  as  at 
B.  A  smooth  curve  drawn  through 
the  points  found  will  give  the  projec- 
tion of  the  helix,  as  at  C. 

The  application  of  the  helix  is 
shown  in  Fig.  142,  which  is  the  actual 
projection  of  a  square  thread.  Such 
drawings  are  seldom  made  as  they 
require  too  much  time  and  are  no  T~ 
better  practically  than  the  conven-  J  5 
tional  representations  commonly  used. 
For  diameters  of  more  than  one  inch 
the  representations  of  Fig.  143  may 
be  used.  The  order  of  drawing  the 
lines  for  V  threads  is  shown  in  Fig. 
144. 

For  small  diameters  the  representa- 
tion is  further  conventionalized  to 
one  of  the  forms  of  Fig.  145.  The 
pitch  or  distance  between  threads  is 
not  measured  but  the  lines  are  spaced 
so  as  to  look  well,  as  indicated  in  the 
figures.  The  simple  form  shown  at  C 
is  generally  satisfactory  and  is  easily 
and  quickly  made. 

Screw  threads  in  section  are  shown  in  Fig.  146.  Threaded 
holes  in  plan,  elevation  and  section  may  be  drawn  as  in  Fig. 
147.  Any  one  of  the  plan  representations  may  be  used  with  any 
of  the  elevations  or  sections.  A  small  threaded  hole  is  called  a 
"tapped"  hole  and  a  note  such  as  "tap  for  %"  U.  S.  Std.  Thread" 
placed  on  the  drawing.  If  a  threaded  hole  does  not  go  clear 


WfiJTWOPTH 


SQUARE 


KNUCKLE 
FIG.  139.— Threads. 


72 


MECHANICAL  DRAWING 


FIG.  140.— Helix. 


i    r : 


T     FIG.   141. — Drawing   a^helix. 


FIG.  142. — True  projection  of  square  thread. 


A  B 

FIG.   143.— Straight  line'thread  representations. 


* 


TECHNIC  OF  THE  FINISHED  DRAWING 


FIG.   144. — Order  of  drawing  a  V  thread. 


A 


•fc 

a< 

// 

Fl 


FIG.   145. — Usual  methods  of  drawing  threads. 


FIG.   146. — Threads  in  section. 


FIG.   147. — Various  methods  of  drawing  threaded  holes. 


74 


MECHANICAL  DRAWING 


through  a  piece  the  "drill  point "  or  shape  of  the  bottom  of  the 
hole  should  be  drawn  as  shown. 

72.  Bolts  and  Other  Fastenings. — The  various  kinds  of  bolts, 
screws,  and  rivets  used  for  fastening  parts  together  occur  on  so 
many  drawings  that  the  draftsman  must  know  what  kind  of 
fastenings  to  use  and  how  to  represent  them  conventionally. 
In  the  previous  paragraphs  the  methods  of  representing  threads 
conventionally  have  been  shown.  These  are  always  used  on 
shop  drawings  on  account  of  the  saving  of  time. 

There  are  many  forms  of  bolts  made  for  different  purposes. 
The  ones  which  we  must  be  familiar  with  are  the  United  States 
Standard  hex  head  and  square  head  bolts  and  nuts.  The  number 
of  threads  per  inch  is  standard  for  each  diameter.  Data  for  U.  S. 
Standard  bolts  and  nuts  is  given  in  Table  I. 


TABLE  I. — DIMENSIONS  OP  U.  S.  STANDARD  BOLTS  AND  NUTS 


Diam. 

of  bolt, 

in. 


Threads 
per 
inch 


Diam.  at 
root  of 
thread 


Area  at 
root  of 
thread 


Distance 

across 

flats,  in. 


Distance 
across  corners 


Hexagon, 


Square, 


Thickness 


Nut, 
in. 


Head, 
in. 


X 

H 
KG 

X 
X 


IX 
IX 

IX 

2 


20 
18 
16 
14 
13 
12 
11 
10 

9 

8 

7 

7 

6 

6 

5 

4% 


0.185 
0.241 
0.294 
0.345 
0.400 
0.454 
0.507 
0.620 
0.731 
0.838 
0.940 
1.065 
1.159 
1.284 
1.490 
1.711 


0.026 
0.045 
0.068 
0.093 
0.126 
0.162 
0.202 
0.302 
0.420 
0.551 
0.693 
0.889 
1.054 
1.293 
1.744 
2.300 


x 


1X4 
IX 


1X4 

IX 

IX 


IX 


2 

2^6 


2%2 

2%  6 

2% 

2% 

3^6 


2^2 
2^4 

2%6 


3^2 


X 

Ke 

Me 
X 

* 
1 

IX 
IK 

IX 
IX 

2 


X 


1 
IXz 

iMe 


Both  hex  and  square  forms  have  the  same  dimensions  "  across 
flats,"  which  is  equal  to  one  and  one-half  times  the  diameter  of 
the  bolt  plus  %",  oTS  =  l%d  +  %". 

The  thickness  of  a  bolt  head  is  one-half  the  distance  across 


TECHNIC  OF  THE  FINISHED  DRAWING 


75 


o 

flats  or  =  ~-     The  thickness  of  a  nut  is  equal  to  the  diameter, 
« 

=  d. 


FIG.  148. — To  draw  a  hexagon. 

73.  To  Draw  a  Bolt. — The  easiest  way  to  understand  a  bolt 
head  is  to  draw  the  top  and  front  views.  Since 
the  hexagonal  form  is  oftenest  used  we  must 
know  how  to  draw  a  regular  hexagon. 

To  Draw  a  Hexagon. — Given  the  distance 
between  two  sides,  called  the  short  diameter, 
or  "distance  across  flats, "  Fig.  148.  First 
draw  horizontal  and  vertical  center  lines. 
With  the  intersection  as  a  center,  draw  a  cir- 
cle having  a  diameter  equal  to  the  distance 
across  flats.  With  the  T-square  and  30°-60° 
triangle,  draw  lines  tangent  to  the  circle  in 
the  order  given. 

A  hex  bolt  head  is  a  hexagonal  prism  with 
the  corners  chamfered  as  shown  in  the  picture 
of  Fig.  138. 

74.  To  Draw  a  Bolt  Head.— Start  the  top 
view  by  drawing  the  chamfer  circle  with  a 
diameter  equal  to  one  and  one-half  times  the 
diameter  of  the  bolt  plus  one-eighth  of  an  inch. 
S  =  1%  d  -f-  %".  About  this  circle  draw  a 
hexagon  as  just  described.  For  the  front 
view  draw  a  horizontal  line  representing  the 
under  side  of  the  head.  The  thickness  of  the 

cr 

head  is  ~>  or  the  radius  of  the  chamfer  circle. 

Draw  top  line  and  project  from  top  view 
Complete  the  front  view  by  drawing  three 
The  middle  arc  has  a  radius 


FIG.   149. 


to  obtain  edges. 

circle  arcs  as  shown  in  Fig.  149. 


76 


MECHANICAL  DRAWING 


equal  to  d  and  the  side  arcs  are  of  such  radius  as  to  line  across 
with  the  middle  one.  Their  centers  may  be  found  by  the  con- 
struction shown,  but  draftsmen  often  draw  the  arcs  by  trial, 
without  construction. 


p 

^ 

/I 

> 

/  > 

£ 

/v     > 

>     /    1 

?      V     > 

=  d=  Djafr?  of  3o/f 

x.x 

/***  found  /by  trio/ 


E\     yv    \     vv    \  s+ 

r^-+-^^\          C 

FIG.     150. — To  draw  a  U.  S.  Standard  hex  head  and  nut. 


r 


E  C 

FIG.   151. — To  draw  a  U.  S.  Standard  square  head  and  nut. 

75.  In  drawing  a  bolt  head  or  nut  it  is  not  necessary  to  draw 
the  top  view.  A  convenient  method  of -drawing  bolts  and  nuts 
is  illustrated  in  Fig.  150,  where  a  simple  diagram  is  used  to  obtain 


TECHNIC  OF  THE  FINISHED  DRAWING 


77 


the  dimensions.  To  draw  the  diagram  shown  at  A,  lay  off  on 
a  horizontal  line  the  diameter  of  the  bolt,  half  the  diameter  of  the 
bolt  and  J^/7.  From  one  end  of  the  line  draw  a  30°  line  with 
the  triangle  and  from  the  other  end  draw  a  vertical  line. 
Complete  the  diagram  as  shown.  The  distances  are  marked  on 


~^ 

t 

~^\ 

1 

1 

"  '  *^r 
* 

1 

—4 

r— 

^>~ 

-> 

<" 

, 

FIG.   152. — Dimensioning  a  Standard  bolt. 


FIG.  153. — A  stud. 


the  diagram  to  correspond  with  the  same  distances  on  the  bolt 
head  and  nut. 

Figure  151  shows  the  same  method  applied  to  a  square  head 
bolt  and  nut,  in  which  the  diagram  is  constructed  with  a  45° 
angle  instead  of  30°. 

The  proportions  of  bolt  heads  and  nuts  are  so  well  standardized 
that  they  are  not  dimensioned  on  a  drawing.  For  a  bolt  it  is 

only  necessary  to  specify  three 
dimensions,  the  diameter,  length 
from  under  side  of  head  to  end  of 
bolt,"  and  length  of  thread,  as  in 
Fig.  152. 

A  stud  or  stud  bolt,  Fig.  153,  has 
threads  on  both  ends  and  is  used 
where  bolts  are  not  suitable  and 
for  parts  which  must  be  removed 
often.  One  end  is  screwed  perma- 
nently into  a  tapped  hole  and  a  nut 
is  screwed  on  the  projecting  end. 

Various  arrangements  are  used 
to  prevent  nuts  from  working  loose 
under  vibration.  Locknuts  such  as  illustrated  in  Fig.  154,  are 
the  commonest. 

76.  S.  A.  E.  Standard  Bolts. — Bolts  used  for  automobile  work 
have  finer  threads,  and  smaller  heads  and  nuts  than  U.  S.  Stand- 
ard. A  pin  through  the  bolt  is  used  to  prevent  loosening  of  the 


]' 

/ 

/ 

— 
1 

1 

--d 
1 
1 

I 

» 

1 

1 
| 

1 

1 

\ 

i 

\ 

\          \ 

FIG.   154. — Locknuts. 


78 


MECHANICAL  DRAWING 


"castle  nut"  and  the  head  is  slotted  for  the  use  of  a  screw  driver. 
The  dimensions  for  the  standard  of  the  Society  of  Automotive 
Engineers  is  given  in  Table  II. 


TABLE  II.  —  DIMENSIONS  OF  S.  A.  E.  STANDARD  BOLTS  AND  NUTS 


^xJ   J=( 1... 


Threads 


K 


KG 

H 

KG 


28 
24 
24 
20 
20 
18 
18 
16 
16 
14 
14 


KG 


5/32 


5/32 
5/32 
5/32 


KG 


y± 

H 


He 


3/32 


y8 
y8 
y8 
y8 

y8 


KG 
KG 


15/32 

KG 
3A  ' 


S/32 


77.  Cap  screws  have  various  forms  of  heads  and  are  used  for 
fastening  two  pieces  together  by  passing  through  one  and  screw- 
ing into  a  tapped  hole  in  the  other.  The  usual  range  of  sizes 
and  dimensions  for  drawing  are  given  in  Table  III. 

Machine  screws  are  used  where  small  diameters  are  required, 
they  are  specified  by  number  and  run  from  No.  0  (.06"  diam.) 
to  No.  30  (.45"  diam.).  They  are  similar  to  cap  screws  in 
appearance. 


TECHNIC  OF  THE  FINISHED  DRAWING  79 

TABLE  III. — DIMENSIONS  OF  CAP  SCREWS 


Hexagor, 


Square          Ortt  ft///ster     P/af  Fillte'er          Button  Counfersunk 


D     K 


He      K 


Ke 


I  He 


IK  i  IK 


He 
K2 
K 


K 
He 


K 
« 
Ke 


H 

ni 

He 


M 


H 

He 


1 
IK 

He 


Set  screws,  Fig.  155,  are  used  for  holding  two  parts  in  a  desired 
position  relative  to  each  other  by  screwing  through  a  threaded 
hole  in  one  piece  and  bearing  against  the  other. 


-o 


K£GULAfi  LOW  HEAD  HEADLESS 

FIG.  155. — Set  screws. 


SAFETY 


78.  Wood  screws  are  made  of  steel  or  brass,  and  are  finished 
in  various  ways.  Steel  screws  may  be  bright  (natural  finish), 
blued,  galvanized  or  copper  plated,  while  both  steel  and  brass 
are  sometimes  nickel  plated.  Round  head  screws  have  the  head 
above  the  wood  while  flat  head  screws  are  set  flush,  or  counter- 
sunk. They  are  drawn  as  in  Fig.  156.  Wood  screws  are  speci- 
fied by  length,  style  of  head,  number,  and  finish.  Length  of 


80 


MECHANICAL  DRAWING 


flat  head  screws  is  measured  over  all  and  round  head  screws 
from  under  head  to  point.  A  lag  screw,  drawn  as  in  Fig.  157,  is 
used  for  fastening  machinery  to  wood  supports  and  for  heavy 
wood  constructions  when  a  bolt  cannot  be  used.  It  is  similar  to 
a  machine  bolt  but  has  wood  screw  threads.  The  head  may  be 

either  square  or  hexagonal.  Lag 
screws  are  specified  by  diameter 
and  length  from  under  side  of 
head  to  end  of  screw. 


FIG.   156. — Wood  screws,  as  drawn. 


FIG.   157. — Lag  screw. 


Several  other  forms  of  screws  and  bolts  are  drawn  as  in  Fig. 
158.  Screw  hooks  and  screw  eyes  are  specified  by  diameter  and 
length  over  all. 

79.  Conventional  Symbols. — There  are  a  number  of  commonly 
accepted  symbols  used  on  drawings.  The  symbols  for  represent- 


Hanger  Bo/t  Drive  Screw 

fi '     FIG.  158. — Various  bolts  and  screws 

ing  the  cut  surfaces  of  sectional  views  as  given  by  a  committee 
•of  the  American  Society  of  Mechanical  Engineers  are  shown  in 
Fig.  159.  For  showing  the  cross-section  of  long,  uniformly 
shaped  pieces  and  for  "breaking  out"  parts  the  representations 
of  Fig.  160  are  used. 


TECHNIC  OF  THE  FINISHED  DRAWING 


81 


Rock  Origino/       Filling  Sand  Other' frlater/a/s 

Earth 

FIG.  159. — Symbols  for  materials  in  section  (A.  S.  M.  E.). 
i 


ROLLED  SHAPES 


ROPE  OR  CABLE 


<XJ|  |     |  |-  CXI 


BEARING 


XLJBffl) 

^SQUARE  SECTION 


FIQ.  160.— Conventional  breaks  and  other  symbols. 


82  MECHANICAL  DRAWING 

80.  Blueprinting. — Practically  all  work  in  shops  or  on  struc- 
tures is  done  from  blueprints,  which  are  copies  made  from  a  trac- 
ing, on  chemically  treated  paper,  giving  white  lines  on  a  blue 
background.  As  many  copies  as  desired  can  be  made  from  a 
single  tracing.  Blueprints  can  be  made  from  pencil  or  ink 
drawings  on  tracing  cloth,  tracing  paper  or  bond  paper.  The 
original  drawing  is  never  allowed  to  go  into  the  shop  but  is  kept 
in  the  files  of  the  drawing  room.  Blueprint  paper  is  usually 
bought  ready  sensitized  and  may  be  had  in  different  degrees  of 
rapidity,  when  fresh  it  is  of  a  yellowish  green  color  and  an  un- 
exposed  piece  should  wash  out  perfectly  white,  with  age  or  ex- 
posure to  light  or  air  it  turns  to  a  darker  gray  blue  color,  and 
spoils  altogether  in  a  comparatively  short  time. 


Blue-print  frame. 

81.  To  Make  a  Blueprint. — Place  the  tracing  in  a  blueprint 
frame  with  the  inked  side  next  to  the  glass  and  lay  a  sheet  of 
blueprint  paper  with  the  sensitized  side  next  to  the  tracing.  Put 
the  back  of  the  frame  in  place  and  lock  it  in  position  so  as  to 
hold  the  tracing  and  paper.  Expose  to  sunlight  or  electric  light 
for  from  30  seconds  to  several  minutes,  depending  upon  the 
sensitiveness  of  the  paper.  The  yellowish  green  color  of  the 
unexposed  paper  will  turn  to  a  grayish  color.  Take  the  paper 
from  the  frame  and  wash  in  a  bath  of  running  water  for  five  or 
ten  minutes.  This  fixes  the  blue  color  and  washes  the  lines  to  a 
clear  white.  Hang  up  until  dry.  The  prints  may  be  improved 
in  color  and  clearness  by  dipping  in  a  dilute  bath  of  sodium 
bichromate  or  hydrogen  peroxide  and  rinsing  after  taking  from 
the  original  bath.  Changes  may  be  made  on  blueprints  by  using 
any  alkaline  solution  in  a  writing  or  drawing  pen. 


TECHNIC  OF  THE  FINISHED  DRAWING  83 

NINETEEN  NEVERS 

1.  Never  begin  work  without  wiping  off  table  and  instru- 
ments. 

2.  Never  use  the  scale  as  a  ruler. 

3.  Never  use  a  dull  lead  pencil. 

4.  Never  draw  with  the  lower  edge  of  the  T-square. 

5.  Never  put  either  end  of  a  pencil  into  the  mouth. 

6.  Never  take  dimensions  by  setting  the  dividers  on  the 
scale. 

7.  Never  run  backward  over  a  line  either  with  pencil  or  pen. 

8.  Never  try  to  use  the  same  thumb  tack  holes  when  putting 
paper  down  a  second  time. 

9.  Never  use  a  blotter  on  inked  lines. 

10.  Never  leave  the  ink  bottle  uncorked. 

11.  Never  dilute  ink  with  water.     If  too  thick  throw  it  away. 

12.  Never  put  a  writing  pen  which  has  been  used  in  ordinary 
writing  ink,  into  the  drawing-ink  bottle. 

13.  Never  scrub  a  drawing  all  over  with  the  eraser  after 
finishing.     It  takes  the  life  out  of  the  inked  lines. 

14.  Never  cut  paper  with  a  knife  and  the  edge  of  the  T-square 
as  a  guide. 

15.  Never  use  the  T-square  as  a  hammer. 

16.  Never  jab  the  dividers  into  the  drawing  board. 

17.  Never  use  the  dividers  as  reamers  or  pincers  or  picks. 

18.  Never   put   instruments   away   without   cleaning.     This 
applies  with  particular  force  to  pens. 

19.  Never  put  bow  instruments  away  without  opening  to 
relieve  the  spring. 


CHAPTER  VI 
DRAFTING,  MECHANICAL  AND  ARCHITECTURAL 

82.  Working  Drawings. — A  working  drawing  is  a  drawing 
which  completely  describes  the  shape  and  size,  and  gives  speci- 
fications for  the  kinds  of  material,  methods  of  finish,  accuracy 
required  and  all  other  information  necessary  for  making  a  single 
part,  or  a  complete  machine  or  structure. 

Working  drawings  are  based  upon  orthographic  projection, 
Chapter  III,  with  dimensions  and  notes  added  as  described  in 
Chapters  IV  and  V.  A  working  drawing  may  be  made  for  a  sepa- 
rate piece,  for  a  group  of  pieces,  or  for  a  completely  assembled 
construction. 


::::—--"- ~t ^ ~ V  I 


PLANING  JIG  FOR  TAPER  GIBS 


FIG.  161. — A  detail   drawing. 

83.  Detail  Drawings. — A  drawing  of  a  single  piece  which  gives 
all  the  information  necessary  for  making  it  is  called  a  detail  draw- 
ing. This  is  the  simplest  form  of  working  drawing  and  must  be 
a  very  complete  and  accurate  description  of  the  piece,  with  care- 
fully selected  views  and  well-located  dimensions.  Sometimes 
separate  detail  drawings  are  made -for  the  use  of  different  work- 
men, as  the  patternmaker,  blacksmith,  machinist,  etc.  Such 
drawings  have  only  the  dimensions  and  information  needed  by 
the  workmen  for  whom  the  drawing  is  made. 

84 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        85 


forging,  esf/motecf  tveighf  /533  Lhs. 


Section  xJ-A  Section  B-B  Section  C-C  SecfionD'O 


BLACK  FORGING  FOR  JACKET 
75  MM    FIELD  GUN 


FIG.  162. — A  forging  drawing. 


FIG.  163. — An  assembly  working  drawing. 


86 


MECHANICAL  DRAWING 


An  ordinary  machine  detail  drawing  is  shown  in  Fig.  161,  and 
a  forging  drawing  in  Fig.  162. 

When  a  large  number  of  machines  are  to  be  manufactured,  it 
is  usual  to  make  a  detail  drawing  for  each  part  on  a  separate  sheet. 

84.  Assembly  Drawings. — A  drawing  of  a  completely  assembled 
construction  is  called  an  assembly  drawing.  Such  drawings 
vary  greatly  in  regard  to  completeness  of  detail  and  dimensioning. 
Their  particular  value  is 'in  showing  the  way  in  which  the  parts 


FIG.  164. — An  outline  assembly  drawing,  with  shade  lines. 

go  together  and  the  appearance  of  the  construction  as  a  whole. 
When  complete  information  is  given  they  may  be  used  for  work- 
ing drawings.  This  is  possible  when  there  is  little  or  no  complex 
detail.  Figure  163  shows  such  a  drawing.  Furniture  and  other 
wood  constructions  can  often  be  represented  in  assembly  working 
drawings  by  adding  necessary  enlarged  details  or  extra  partial 
views. 

Assembly  drawings  of  machines  are  generally  made  to  small 
scale  with  selected  dimensions  to  tell  over-all  distances,  important 
center-to-center  distances  and  location  dimensions.  All  or  al- 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        87 


most  all  hidden  lines  may  be  left  out  and  if  to  very  small  scale 
unnecessary  detail  may  be  omitted. 

Either  exterior  or  sectional  views  may  be  used.     When  the 
general  appearance  is  the  main  purpose  of  the  drawing,  only 


\ 


\ 


FIG.  165. — Conventional  shade  lines. 


:  shade 


one  view  or  two  views  may  be  used,  sometimes  with 
lines"  to  bring  out  the  shape  more  clearly,  Fig.  164. 

85.  Shade  Lines. — When  shade  lines  are  used  the  simple 
conventional  method  is  to  shade  the  lower  and  right-hand  lines 
of  each  part  in  all  views.  Assume  parallel  rays  of  light  at 


FIG.  166. — Shade  lines  on  circles  and  arcs. 

an  angle  of  45°  in  the  direction  shown  in  Fig.  165.  Each  view  is 
considered  by  itself.  Edges  over  which  the  rays  of  light  pass  are 
shaded.  Dotted  lines  are  never  shaded.  Light  lines  are  made 
very  fine.  Shade  lines  are  made  at  least  three  times  the  width 


88  MECHANICAL  DRAWING 

of  fine  lines.     The  extra  thickness  of  line  is  added  outside  the 
boundaries  of 'the  view. 

A  circle  is  shaded  by  moving  the  center  of  the  compasses  on  a 
45°  line  toward  the  lower  right-hand  corner  a  distance  equal  to 
the  thickness  of  the  shade  line,  and  drawing  a  tangent  semi-circle 
as  shown  in  Fig.  166. 

86.  Choice  of  Views. — Much  of  the  ease  with  which  a  drawing 
can  be  used  depends  upon  proper  selection  of  views.     For  the 
complete  description  of  an  object  at  least  two  views  are  required. 
While  a  drawing  is  not  a  picture  it  is  always  advisable  to  select 
the  views  which  require  the  least  effort  to  read.     Each  view 
must  have  a  part  in  the  description  or  it  is  not  needed  and  should 
not  be  drawn.     In  some  cases  one  view  is  all  that  is  necessary, 
provided  a  note  is  added  or  the  shape  and  size  is  standard  or 
evident.     Complex  pieces  may  require  more  than  three  views, 
some  of  which  may  be  partial  views,  auxiliary  and  sectional 
views.     The  reason  for  making  the  drawing  must  always  be  kept 
in  mind  when  a  question  arises.     The  final  test  of  the  value  of  a 
drawing  is  its  clearness  and  exactness  in  giving  the  complete 
information  necessary  for  making  the  piece. 

87.  Choice  of  Scale. — The  choice  of  scale  for  a  detail  drawing 
is  governed  by  three  things — the  size  necessary  for  showing  all 
details  clearly,  the  size  necessary  for  carrying  all  dimensions  with- 
out crowding  and  the  size  of  paper  used.     It  is  always  desirable 
to  make  detail  drawings  to  full  size.     Other  scales  commonly 
used  are  half,  quarter,  and  eighth,  see  Art.  13.     Such  scales  as 
2"  =  1',  4"  =  1',  and  9"  =  1',  are  to  be  avoided.     If  a  part  is 
very  small  it  is  sometimes  drawn  to  an  enlarged  scale,  perhaps 
twice  full  size. 

When  a  number  of  details  are  drawn  on  one  sheet  they  should 
if  possible  be  to  the  same  scale.  If  different  scales  are  used  they 
should  be  noted  near  each  drawing.  A  detail  or  part  detail 
drawn  to  a  larger  scale  may  often  be  used  to  advantage  on  assem- 
bly drawings.  This  will  save  the  making  of  separate  detail  draw- 
ings. General  assembly  drawings  can  be  made  to  such  a  scale 
as  will  show  the  desired  amount  of  detail  and  work  up  well  on  the 
size  of  paper  used.  Sheet-metal  pattern  drawings  for  practical 
use  are  always  made  full  size,  although  practice  models  may  be 
constructed  from  small  scale  layouts. 

88.  Grouping  and  Placing  Parts. — When  a  number  of  details 
are  used  for  one  machine  only,  they  are  often  grouped  on  a  single 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        89 

sheet  or  set  of  sheets.  A  convenient  arrangement  is  to  group 
the  forging  details  together,  the  brass  details  together  and  simi- 
larly for  other  materials.  In  general  it  is  well  to  represent  parts 
in  the  position  which  they  will  have  in  the  assembled  machine, 
with  related  parts  near  each  other.  Long  pieces,  however,  such 


FIG.  167. — Rib  in  a  section. 


as   shafts,   bolts,   etc.,  are  drawn  with  their  long  dimensions 
horizontal. 

89.  Conventional  Representation. — The  principles  upon  which 
the  description  of  shape  by  means  of  views  is  based  have  been 
explained  and  they  form  the  basis  for  working  drawings.  In 


FIG.  168. — Pulley  in  section. 

the  actual  use  of  mechanical  drawing  it  has  been  found  desirable 
under  certain  conditions  to  violate  the  rules  previously  given. 

90.  Sections  Through  Ribs,  Arms,  Etc. — When  the  plane  of  a 
section  passes  through  a  rib  or  pulley  arm  the  drawing  is  made 


90 


MECHANICAL  DRAWING 


as  in  Figs.  167  and  168,  where  the  plane  is  thought  of  as  being  just 
in  front  of  the  rib  or  arm.  A  true  section  would  give  the  idea  of  a 
very  heavy  solid  piece.  When  a  section  or  elevation  of  a  drilled 
flange  is  drawn,  the  holes  are  shown  at  their  true  distance  from 
the  center  regardless  of  where  they  would  project,  Fig.  169. 


FIG.  169. — Flanges,  in  elevation  and  section. 

A  revolved  or  turned  section  is  sometimes  inserted  in  a  view  to 
show  the  shape,  as  in  Figs.  170  and  171. 

91.  Rule  of  Contour. — In  general  preserve  the  characteristic 
contour  of  an  object.  Sections  or  elevations  of  symmetrical 
pieces  are  sometimes  hard  to  read  when  drawn  in  true  projection. 
It  is  usual  in  such  cases  to  revolve  a  portion  of  the  object  until 


FIG.  170. — Revolved   section. 


FIG.  171. — Revolved  section. 


the  characteristic  contour  shows.     This  has  been  done  in  Fig. 
172,  which  is  the  correct  method  of  drawing  the  object  shown. 

It  is  always  desirable  to  show  true  distances  even  though  the 
views  do  not  project.  This  may  be  illustrated  by  bent  levers 
and  similar  pieces  which  are  represented  by  revolved  or  stretched 
out  views  as  in  Fig.  173 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        91 


92.  Gears. — If  two  wheels  are  in  contact  and  keyed  to  parallel 
shafts,  both  will  revolve  if  either  one  of  the  shafts  is  turned,  Fig. 
174.  If  the  driven  shaft  turns  hard  the  wheel  will  slip.  To 


FIG.  172. — The  "rule  of  contour." 

prevent  slipping,  teeth  are  added  to  the  wheels.  The  shape  of 
these  teeth  is  such  that  the  same  kind  of  motion  as  with  the 
rolling  wheels  is  obtained.  Gearing  is  a  separate  study  but  the 
student  should  know  how  to  show  a  gear  on  a  drawing.  Spur 


FIG.  173. — A  stretched  out  view. 


gears  and  bevel  gears,  Figs.  175  and  176  are  the  most  common 
forms.  A  small  gear  used  with  a  large  one,  .or  with  a  "rack"  is 
called  a  " pinion."  The  parts  of  gear  teeth  have  names  as  given 


92 


MECHANICAL  DRAWING 


in  Fig.  177.  There  are  three  diameters  and  two  kinds  of  pitch  to 
remember.  The  three  diameters  are  indicated  on  the  figure. 
The  circular  pitch  is  the  distance  from  a  point  on  one  tooth  to 
the  same  point  on  the  next  tooth,  measured  along  the  pitch  circle. 


Outside  Diameter 
'oof  Diameter 


FIG.  174. 


PINION  RACK 

FIG.  175. — Spur  gears. 


Let  N  =  number  of  teeth 

D  =  diameter  of  pitch  circle 
Pc  =  circular  pitch 
P  =  diameter  pitch 

Addendum  =  - 
Dedendum  =  —  + 


Width  of  Face 


Circular  Pitch 


FIG.  176. — Bevel  gears. 


FIG.  177. 


The  diameter  pitch  is  a  number  found  by  dividing  the  number  of 
teeth  by  the  diameter  of  the  pitch  circle. 

It  is  not  necessary  to  draw  the  actual  teeth  when  making  work- 
ing drawings  of  gears.  Cut  spur  and  bevel  gears  are  drawn  as  in 
Figs.  178  and  179,  which  show  "gear  blanks"  with  notes  to  give 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        93 

required  information.     The  representations   of    Fig.    180    are 
used  on  assembly  drawings. 

93.  Cams. — A  cam  is  a  machine  element  used  to  obtain  an 
irregular  or  special  motion  not  easily  obtained  by  other  means. 


/OP..  43  T: 

DEPTH  OF  CUf.Z/6  * 

FIG.  178. — Working  drawing  of  a  cut  spur  gear. 


5  P/TCH  -  35  TEETH 

finish  a//  over 

FIG.  179. — Working  drawing  of  a  cut  bevel  gear. 


The  shape  of  a  cam  is  derived  from  the  motion  required  of  it. 
One  form  of  plate  cam  is  shown  in  Fig.  181.  A  cylindrical  cam 
is  shown  in  Fig.  182. 


94 


MECHANICAL  DRAWING 


FIG.  180. — Gears  in  elevation. 


FIG.  182.— A  cylindrical  cam. 


FIG.  183. — Drawing  of  plate  cam. 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        95 

To  find  the  cam  outline,  Fig.  183,  given  point  C,  the  center  of 
the  shaft  and  point  A,  the  lowest  position  of  the  center  of  the 
roller.  It  is  required  to  raise  the  center  of  the  roller  with  uni- 
form motion  during  three-eighths  of  a  revolution  of  the  uniformly 
revolving  shaft,  allow  it  to  drop  two-thirds  of  the  way  down  in- 
stantly, remain  at  rest  for  one-eighth  of  a  revolution,  drop  uni- 
formly during  three-eighths  of  a  revolution,  and  remain  at  rest  for 
the  remaining  one-eighth  of  a  revolution. 

Divide  the  rise  into  a  number  of  equal  parts.  Divide  the  arc 
ADE  into  the  same  number  of  equal  spaces  as  there  are  spaces 
in  the  rise,  and  draw  radial  lines.  With  C  as  a  center  and  radius 
Cl  draw  an  arc  intersecting  the  first  radial  line  at  1'.  In  the 
same  way  locate  points  2',  3',  etc.,  and  draw  a  smooth  curve 
through  them.  If  the  cam  is  revolved  in  the  direction  of  the 
arrow,  it  will  raise  the  roller  with  the  desired  motion.  Draw 
B'J  equal  to  two-thirds  of  AB.  Draw  arc  JK  with  radius  CJ. 
Divide  A2  into  six  equal  parts  and  arc  FGH  into  six  equal  parts. 
Circle  arcs  drawn  as  shown  will  locate  points  on  the  cam  outline. 
Draw  arc  HA  with  radius  CH  to  complete  the  cam.  This  out- 
line is  for  the  center  of  the  roller,  allowance  for  which  may  be 
made  by  drawing  the  roller  in  its  successive  positions  and  then 
drawing  the  tangent  curve  as  shown  in  the  auxiliary  figure. 

ARCHITECTURAL  DRAWING 

94.  Architectural  Drawing. — All  kinds  of  technical  drawing 
are  based  upon  the  same  general  principles.  Architectural 
drawings  have  to  do  with  the  representation  and  specification 
of  buildings.  The  drawing  of  a  building  has  to  be  made  to  a 
very  small  scale  as  compared  with  a  machine  drawing,  which 
makes  it  necessary  to  use  conventional  symbols  for  the  different 
parts.  They  differ  also  in  that  only  one  view  usually  is  drawn 
on  a  sheet. 

There  are  three  general  classes  of  architectural  drawings: 

1.  Preliminary  sketches:  These  are  freehand  studies  of  the 
arrangement  of  rooms,  first  made  as  very  small  "thumb-nail" 
sketches  without  using  the  scale,  and  when  a  satisfactory  scheme 
is  decided  upon,  worked  up  in  larger  freehand  sketches  to  ap- 
proximate scale. 

2.  Display  and  competitive  drawings:  These  are  more  or  less 
elaborate  preliminary  drawings  of  a  proposed  building,  often 


96 


MECHANICAL  DRAWING 


including  a  perspective,  and  are  rendered  in  water-color,  pen-and- 
ink,  or  pencil  to  make  them  legible  and  attractive  . 

3.  Working  drawings:  These  form  the  most  important  class, 
and  include  plans,  elevations,  sections  and  detail  drawings  which 
when  read  with  the  specifications  for  details  of  materials  and 


FIG.  184. — Sketch  plan. 

finish,  give  [the  ^working  information  for  the  erection  of  the 
building. 

95.  Plans. — A  floor  plan  is  a  horizontal  section  taken  above 
the  floor  represented.  It  shows  all  the  walls  with  their  doors  and 
windows,  gives  the  location  of  lighting,  heating  and  plumbing 


FIG.  185. 

outlets,  and  shows  part  of  the  stairways  starting  up  or  down 
from  the  floor.     A  plan  is  always  laid  out  with  the  front  of  the 
building  at  the  bottom  of  the  sheet.     Ordinary  house  plans  are 
drawn  to  the  scale  of  Y±'  =  V . 
Fig.  184  is  a  freehand  sketch  plan  of  the  first  floor  of  a  house. 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        97 


98 


MECHANICAL  DRAWING 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL        99 


1 


100 


MECHANICAL  DRAWING 


DRAFTING,  MECHANICAL  AND 


!l62 ; ;  5  j  itfECjIANICAL  DRAWING 


'oQ^ 

•ss 

•  u  - 


DRAFTING,  MECHANICAL  AND  ARCHITECTURAL      103 

With  this  as  a  basis  it  is  required  to  draw  the  plans  of  the  house. 
The  first  floor  as  shown  in  Fig.  187,  is  drawn  first,  then  the 
second  floor  and  basement  plans.  Draw  a  horizontal  line  rep- 
resenting the  outside  face  of  the  front  wall.  Complete  the 
exterior  walls  and  interior  partitions.  Frame  walls  are  drawn 
6"  thick. .  Locate  doors  and  windows  and  draw  them  with  the 
conventional  symbols  as  shown. 

96.  In  drawing  the  stairway  first  make  a  diagram  to  find  the 
number  of  steps  and  space  required.     The  rise,  or  height  from 
one  step  to  the  next,  is  from  6^"  to  7K"  and  the  tread  so 
that  the  sum  of  rise  and  tread  is  about  17J£  inches.     On  the 
plan  the  lines  drawn  represent  the  edges  of  the  risers  and  are 
drawn  as  far  apart  as  the  width  of  the  tread,  as  shown  in  Fig. 
185.     The  entire  flight  is  not  drawn  on  the  plan  but  is  broken  so 
as  to  show  what  is  on  the  floor  under  it.     The  other  end  is  shown 
on  the  plan  of  the  floor  above. 

97.  The  second  floor  for  a  two  story  house  is  best  planned  by 
laying  a  piece  of  tracing  paper  over  the  first  floor  plan.     Trace 
the  exterior  walls  and  locate  stairways  and  chimney  flues.     The 
interior  partition  walls  need  not  be  continuous  with  the  first 
floor.     See  that  closets  are  provided  for  every  room.     Note 
that  the  second  floor,  Fig.  188,  is  for  a  cottage  type  and  account 
must  be  taken  of  headroom  under  the  roof. 

The  basement  plan  is  shown  in  Fig.  186.  It  should  be  com- 
pletely dimensioned  as  the  construction  of  the  house  is  started 
with  this  plan.  Windows  should  be  under  the  first  floor  windows. 
The  furnace  should  be  near  the  center  of  the  house. 

98.  Elevations  and  Sections. — A  front  and  one  side  elevation 
are  shown  in  Figs.  189  and  190.     In  a  complete  set  of  plans  the 
other  side  and  rear  elevations  should  be  drawn.     In  drawing 
elevations  start  with  the  grade  line  as  a  base  line.     The  figures 
show  the  information  usually  given  on  elevations.     A  wall  sec- 
tion to  a  larger  scale  is  shown  in  Fig.  189. 

99.  Details. — In  addition  to  the  quarter-inch  scale  drawings, 
larger  scale  drawings  are  made  of  such  parts  as  cannot  be  shown 
with  sufficient  detail  on  the  small  scale  drawings.     Figure  191  is 
a  typical  sheet  of  details.     As  the  building  progresses  the  archi- 
tect furnishes  full  size  drawings  made  with  soft  pencil,  for  mill- 
work  and  other  details. 

100.  Symbols. — The  usual  symbols  for  doors,  windows,  fire- 
places, etc.,  have  been  shown  on  the  plans.     Different  building 


104 


MECHANICAL  DRAWING 


materials  are  indicated  in  section  as  shown  in  Fig.  192,  and  some 
of  the  standard  wiring  and  lighting  symbols  in  Fig.  193.    - 


'ROY6H'LVM5El'lfi$KTION' 


-"     ..     "     ..     "- 


•BRI(K'iri'ELEVATIOrHAR6E'$(AlE' 


•FRAME -WALL- in-SECTIOri'  •CEMEHWLASTEfcirt'SECTIOM'          aEttKOTTA'WAlblN -SECTION' 

FIG.  192. — Symbols  for  building  materials. 


Outlet;  Electric  only  Numeral 
in  center  indicates  number  of 
Standard  16  C.f  Incandescent  Lamps. 

Cei/ing  Outlet;  Combination  £  indicates 
4--I6CP  Standard  Incandescent 
Lamps  and  2  Gas  Lamps 


Ceiling  Outlet     G-**  On/y. 


Drop  Cord  Ot/t/et. 


tan 


Bracket  Outlet;  Electric  only.  Numeral 
in  center  indicates  number  of 
Stahdara'  If.Cf  Incandescent  Lomf*s 

Bracket  Outfet:  Combination  £  tnaf (cotes 
4-/6  C.f 'Standard  Incandescent 
Lamps  and  2   Gas  t-a/r>/os. 


BracAsf  Oi/t/ef;  Gas  on/y 


r~/oor  Out /ft ;  Numeral  in  center 
ind/catvs  nt/mber  of  Standard 
16  C.P  /ncantfescenf  Lamps- 


Bel/  Ovttcf     ^=|      Te/ephone  Ovt/ct 

FIG.  193.—  Symbols. 


Lettering  on  architectural  drawings  is  usually  done  in  light 
single-stroke  Roman  as  shown  in  Fig.  36. 


CHAPTER  VII 
GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING 

101.  Our  study  of  drawing  in  the  preceding  chapters  has  con- 
sidered two  main  purposes — shape  and  size  description  of  space 
constructions.     There  are,  however,  many  other  ways  of  using 
drawing  as  a  means  of  solving  the  problems  which  arise  in  indus- 
trial work.     Graphic  solutions  require  a  working  knowledge  of 
some  geometrical  constructions  as  the  basis  for  the  "laying  out" 
of  wood  and  metal  work  as  well  as  for  sheet-metal  drafting. 

102.  Lines. — A  line  may  be  divided  into  two  equal  parts  by 
measurement  with  the  scale,  by  trial  with  the  dividers,  or  geomet- 
rically as  in  Fig.  194.     Given  the  line  AB.     Draw  arcs  with  A 


FIG.  194. — To  bisect  a  line.  FIG.  195. — To  divide  a  line. 

and  B  as  centers  and  a  radius  greater  than  one-half  AB.  A  line 
drawn  through  the  intersections  of  the  arcs  will  be  perpendicular 
to  AB  and  will  divide  it  into  two  equal  parts,  or  " bisect"  it. 

103.  A  line  may  be  divided  into  any  number  of  equal  parts  by 
trial  with  the  dividers,  as  described  in  Art.  14,  or  by  using  the 
scale  as  described  in  Art.  15.     Another  way  is  by  the  geometrical 
method  of  Fig.  195.     To  divide  the  line  AB  into  five  equal  parts. 
From  B  draw  another  line  at  an  angle.     On  it  step  off  five  equal 
spaces  of  any  convenient  length.     Connect  the  last  point  (c) 
with  A.     Through  the  other  points  draw  lines  parallel  to  CA, 
using  triangle  and  T-square  as  shown  in  Fig.  9. 

104.  Sometimes  it  is  necessary  to  reduce  or  enlarge  linear 
dimensions  from  one  size  to  another.     A  special  scale  for  this 
purpose  may  be  made  geometrically  on  the  well-known  theorems 
of  proportional  triangles.     Draw  two  parallel  lines  at  a  con- 
venient distance  apart,  one,  A  B,  to  the  given  scale  and  the  other, 

105 


106 


MECHANICAL  DRAWING 


CD,  to  the  desired  length,  either  shorter,  Fig.  196,  or  longer, 
Fig.  197.  Lines  through  AC  and  BD  will  intersect  at  point  0. 
Draw  lines  from  point  0  through  each  division  of  the  given  scale 
AB.  These  will  divide  CD  into  proportional  spaces,  thus  making 
a  new  scale,  Figs.  198  and  199,  from  whichjthe  desired  measure- 
ments can  be  taken. 


o    o 


Reducing 


FIG.   196. 


Enlarging 


FIG.  197. 


FIG.  198. 


FIG.  199. 


FIG.  200.— A  protractor. 

105.  Angles. — When  two  lines  meet  at  a  point  they  form  an 
angle.  Lines  which  are  perpendicular  to  each  other  form  right 
angles.  If  a  right  angle  is  divided  into  90  equal  parts,  each  part 
is  called  a  degree.  A  circle  contains  360  degrees.  An  angle  is 
measured  in  degrees. 

In  Art.  7  we  learned  that  angles  varying  by  15  degrees  may 
be  constructed  with  the  30-60  and  45°  triangles. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   107 

For  measuring  and  laying  out  angles  an  instrument  called  a 
protractor  is  used.  The  usual  form  is  semicircular  as  shown  in 
Fig.  200. 

106.  An  angle  of  90°  may  be  jeadily 
bisected  by   using   the  45°  triangle  or 
trisected  with  the  30-60°  triangle.     To  0. 
bisect  any  angle,  Fig.  201.     With  0  as 
a  center  and  any  radius,  draw  an  arc 
cutting  the  sides  at  A   and  B.     With 
A    and  B  as   centers   and    any   radius 
greater  than  one-half  AB,  draw  intersecting  arcs.     A  line  through 
this  intersection  and  point  0  will  bisect  the  angle. 

A/ew position  of  tvrfex O 


FIG.    201.— To    bisect    an 
angle. 


Mew pos/fton  of        / 
one  side  ofangfe  ^ 


FIG.  202. — To  copy  or  transfer  an  angle. 


107.  To  copy  an  angle,  Fig.  202.  Given  the  angle  AOB. 
Draw  an  arc  with  0  as  a  center  and  any  convenient  radius.  With 
the  same  radius  and  center  at  new  position  0',  draw  another  arc. 

A With   radius    equal    to    chord    DC    and 

center  at  E  draw  an  arc  giving  an  in- 
tersection at  F  through  which  a  line  may 
be  drawn  to  the  vertex  to  complete  the 
angle  in  its  new  position. 

108.  Triangles. — To  construct  a  triangle, 
having  given  the   three   sides,  Fig.  203. 
FIQ.  203.— TO  construct    Given   the   lengths   A,  B  and  C.    Draw 
a  triangle.  one  side  A  in  the  desired  position.     With 

its  ends  as  centers  and  radii  B  and  C  draw  two  intersecting 
arcs  as  shown.  An  equilateral  triangle  has  three  equal  sides. 
It  may  be  constructed  by  drawing  one  side  in  the  desired 


108 


MECHANICAL  DRAWING 


position  and  drawing  intersecting  arcs  with  the  ends  as  centers 
and  the  length  of  the  side  as  a  radius,  Fig.  204.  Another 
method  is  to  draw  60°  lines  from  each  end  of  the  base,  using  the 
30-60°  triangle. 

An  isosceles  triangle  has  two  equal  sides,  Fig.  205.  It  may  be 
constructed  by  locating  the  base  and  drawing  intersecting  arcs 
from  each  end,  using  one  of  the  equal  sides  as  a  radius. 


FIG.  204.— Equilateral 
triangle. 


FIG.  205. — Isosceles 
triangle. 


H 6Vmts — J 


FIG.  206. — Right 
triangle. 


A  right  triangle  is  one  which  has  a  right  angle.  A  right  triangle 
may  be  easily  constructed  by  the  " 6-8-10  method."  Draw  a 
line  6  units  long.  From  one  end  draw  an  arc  with  a  radius  10 
units  long  and  from  the  other  end  with  a  radius  8  units  long. 
Complete  as  shown  in  Fig.  206. 


FIG.  207.— Hexagon. 


FIG.  208.— Hexagon. 


109.  The  Hexagon.— The  regular  hexagon  can  be  drawn  in  a 
number  of  ways  and  has  already  been  explained  in  Art.  73.  If 
the  distance  across  corners  AB  is  given,  draw  a  circle  with  AB 
as  a  diameter,  Fig.  207.  With  A  and  B  as  centers  and  the  same 
radius  draw  arcs  and  connect  points.  A  hexagon  may  be  con- 
structed directly  on  line  AB,  without  using  the  compasses,  by 
drawing  lines  with  the  30-60°  triangle  in  the  order  shown  in  Fig. 
208. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  109 


110.  The  Octagon. — To  draw  an  octagon,  first  draw  a  square. 
Fig.  209.  Draw  the  diagonals  of  the  square.  With  the  corners 
as  centers  and  a  radius  of  half  a  diagonal  draw  arcs  cutting  the 
sides  of  the  square,  and  connect  these  points. 


FIG.  209.— Octagon. 


FIG.  210.— Circle. 


111.  Arcs  and  Tangents. — A  circle  may  be  drawn  through  any 
three  points  which  do  not  lie  in  a  straight  line.  To  draw  a  circle 
through  points  A,  B  and  C,  Fig.  210.  Draw  lines  AB  and  BC. 
Using  the  method  of  Art.  102  bisect  these  lines.  Where  the 
bisectors  cross  at  0  will  be  the  center  for  the  required  circle  for 
which  OA,  OB  and  OC  are  radii. 


FIG.  211.— To  draw  a  tangent. 

112.  To  draw  a  tangent  to  a  circle  at  a  given  point,  Fig.  211. 
Arrange  a  triangle  in  combination  with  the  T-square  (or  another 
triangle)  so  that  its  hypotenuse  passes  through  center  0  and 
point  C.     Holding  the  T-square  firmly  in  place,  turn  the  triangle 
about  its  square  corner,  move  it  until  the  hypotenuse  passes 
through  C,  and  draw  the  tangent. 

113.  To  draw  an  arc  tangent  to  two  lines,  Figs.  212  and  213. 
Given  two  lines  AB  and  CD  and  radius  R.     Draw  lines  parallel 
to  A  B  and  CD  at  a  distance  R  from  them.     The  intersection  of 


110 


MECHANICAL  DRAWING 


these  lines  will  be  the  center  of  the  required  arc.  The  points  of 
tangency  are  found  by  drawing  a  line  through  the  center  of  the 
arc  and  perpendicular  to  the  tangent  lines. 

114.  To  draw  an  arc  tangent  to  two  lines  at  right  angles, 
Fig.  214.     This  case  frequently  occurs  in  drawing  fillets  and 


f 

1* 

1 

v/ 

\ 

A  ff  A 

FIG.  213.  FIG  214. 

To  draw  an  arc  tangent  to  two  lines. 


rounds.  It  is  desired  to  round  the  corner  ABC  with  an  arc 
having  a  radius  equal  to  R.  With  B  as  a  center  and  radius  R, 
draw  an  arc  cutting  the  two  lines.  With  the  points  D  and  E 
thus  found  as  centers  and  the  same  radius  as  before  draw  arcs 
intersecting  at  0.  An  arc  drawn  with  center  0  and  radius  R  will 
be  tangent  to  the  straight  lines  at  points  D  and  E. 


F/rstArc 


FIG.  215. — To  draw  tangent  arcs. 

115.  Sometimes  a  smooth  curve  is  made  up  of  circular  arcs 
having  different  radii.     In  such  cases  we  must  be  very  careful 
to  have  the  arcs  join  at  a  point  of  tangency.     The  two  centers 
and  the  point  of  tangency  are  in  the  same  line,  as  shown  in  Fig. 
215. 

116.  To  lay  off  on  a  straight  line  the  approximate  length  of  a 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   111 


circle  arc,  Fig.  216.  Given  the  arc  AB.  At  A  draw  the  tan- 
gent AD.  Set  the  dividers  to  a  small  space.  Starting  at  B 
step  along  the  arc  to  the  point  nearest  A,  and  without  lifting  the 
dividers  step  off  the  same  number  of  spaces  on  the  tangent,  as 
shown. 

117.  A  reverse  or  "ogee"  curve  is  shown  in  Fig.  217,  joining 
lines  AB  and  CD.  Join  B  and  C  by  a  straight  line.  Draw  pert 
pendiculars  at  B  and  C.  Arcs  tangent  to  lines  AB  and  CD  mus- 
have  their  centers  on  these  perpendiculars.  Point  E  through 
which  the  curve  is  to  pass  may  be  taken  any  place  along  BC. 


FIG.  216. — Length  of  an  arc. 


FIG.  217. — An  ogee  curve. 


Draw  perpendiculars  at  the  middle  points  of  BE  and  EC,  Art. 
102.  Any  arc  to  pass  through  B  and  E  must  have  its  center  on 
a  perpendicular  at  the  middle  point.  The  intersection  therefore 
of  these  perpendiculars  with  the  two  first  perpendiculars  will 
be  the  centers  for  arcs  BE  and  EC.  The  construction  may  be 
checked  by  drawing  the  line  of  centers,  which  must  pass  through 
E. 

118.  The  Ellipse. — If  a  circle  is  parallel  to  a  plane  its  projec- 
tion on  the  plane  will  be  a  circle.  If  it  is  perpendicular  to  the 
plane  its  projection  will  be  a  straight  line.  If  it  is  at  an  angle 
its  projection  will  be  an  ellipse.  A  square  card  with  a  circular 
hole,  drawn  in  different  positions  as  in  Fig.  218  illustrates  the 
above  statements.  jLn  ellipse  is  defined  as  a  curve  generated 
by  a  point  moving  so  that  the  sum  of  its  distances  from  two  fixed 
points,  called^the  foci,  is  constant,  and  is  equal  to  the  longest  diame- 
ter or  major  axis. 

A  line  through  the  center  perpendicular  to  the  major  axis  is 
called  the  short  diameter  or  minor  axis.  To  find  the  foci,  draw 
an  arc  with  center  at  one  end  of  minor  axis  and  radius  equal  to 


112 


MECHANICAL  DRAWING 


one-half  the  major  axis.  This  arc  will  cut  the  major  axis  at  the 
foci,  Fl  and  F2,  Fig.  219. 

There  are  a  number  of  ways  of  constructing  an  ellipse,  two  of 
which  are  given. 

119.  The  easiest  method  for  large  work  is  the  pin-and-string 
method.  Given  the  major  and  minor  axes,  Fig.  220.  Locate 


FIG.  218. — Circle  projected  as  ellipse. 


FIG.  219.— Ellipse. 


the  foci  by  the  method  just  described.  Drive  pins  at  points  Fi, 
C,  and  F2)  and  tie  a  cord  tightly  around  the  three  pins.  If  the 
pin  C  be  removed  and  a  marking  point  moved  in  the  loop,  keep- 
ing the  cord  taut,  it  will  describe  a  true  ellipse. 


FIG.  220. — To  draw  an  ellipse  by  pin-and-string  method. 


120.  A  very  accurate  method  for  finding  the  points  on  an  el- 
lipse is  by  concentric  circles,  Fig.  221.  Draw  two  circles  about 
the  center  of  the  desired  ellipse,  one  with  a  diameter  equal  to 
the  minor  axis  and  the  other  with]  a  diameter  equal  to  the 
major  axis.  Divide  the  large  circle  into  a  number  of  equal 
parts,  and  draw  radii  OP,  OQ,  intersecting  the  small  circle  at  P', 
Q',  etc.  From  P  and  Q  draw  lines  parallel  to  OD,  and  from  P' 


GRAPHIC  SOLUTIONS  AND  SHEET- METAI/DRAFTING  113 

and  Q'  lines  parallel  to  OB.  Where  the  lines  through  P  and  P' 
cross  is  one  point  on  the  ellipse.  The  lines  through  Q  and  Q' 
give  another  point.  In  this  way  each  radial  line  will  locate  a 
point  on  the  ellipse.  For  accuracy  extra  points  should  be  taken 
close  together  toward  the  ends,  where  the  curve  is  changing 
rapidly.  The  curve  is  sketched  in  very  lightly  freehand  before 
drawing  it  in  with  the  irregular  curve.  A  tangent  at  any  point 
H  may  be  drawn  by  dropping  a  perpendicular  from  the  point  to 
the  outer  circle  at  K,  and  drawing  the  auxiliary  tangent  KL 
cutting  the  major  axis  produced,  at  L.  From  L  draw  the  required 
tangent  LH. 


FIG.  221.— Two  circle  method. 


FIG.  222. — Approximate  ellipse. 


121.  Approximate  ellipses  may  be  drawn  with  arcs  of  circles. 
When  the  minor  axis  is  at  least  two-thirds  of  the  major  axis,  the 
four  center  approximation  shown  in  Fig.  222  is  satisfactory.  Make 
OF  and  OG  each  equal  to  AB  minus  DE.  Make  OH  and  01  each 
equal  to  three-fourths  of  OF.  Draw  FH,  FI,  GH  and  GI,  ex- 
tending them  as  shown.  Draw  arcs  through  points  D  and  E 
with  centers  at  G  and  F,  and  through  A  and  B  with  centers  I 
and  H. 


SHEET-METAL  DRAFTING 

122.  Sheet-metal  Drafting. — There  is  a  large  class  of  metal- 
work  made  from  thin  sheets  of  metal,  formed  into  the  required 
shape  by  bending  or  folding  up  and  fastening  by  rivets  or  seams 
or  soldering.  In  this  kind  of  work  the  drawings  consist  of 
the  representation  of  the  finished  object,  arid  the  drawing  of  the 
shape  of  the  flat  sheet,  which  when  rolled  or  folded  and  fas- 


114 


MECHANICAL  DRAWING 


tened  will  make  the  object.1  This  second  drawing  is  called  the 
development  or  pattern  of  the  piece  and  making  it  comes  under 
the  term,  sheet-metal  pattern  drafting. 

123.  Development. — There  are  two  general  classes  of  surfaces, 
plane  surfaces  and  curved  surfaces.  The  six  faces  of  a  cube  are 
plane  surfaces.  The  bases  of  a  cylinder  are  plane  surfaces, 
while  the  lateral  surface  is  curved. 

It  is  possible  to  cut  out  a  piece  of  paper  so  as  to  fold  it  up  into 
a  cube,  as  in  Fig.  223.  The  shape  cut  out  would  be  the  pattern 


FIG.  223.— Pattern  for  a  cube. 


of  the  cube.  Those  who  have  studied  solid  geometry  recall  that 
there  are  five  regular  solids  and  that  their  patterns  are  made  as 
shown  in  Figs.  224  to  228.  A  good  understanding  of  the  nature 
of  developments  may  be  had  by  laying  out  the  above  patterns 
and  folding  them  to  form  the  figures. 

Thus  the  pattern  for  any  piece  which  has  plane  surfaces  may 
be  made  by  first  deciding  where  the  seam  is  to  be,  then  opening 
up  each  face  in  order,  showing  it  in  its  true  size.  One  example, 
the  development  of  a  square  prism,  is  illustrated  in.  Fig.  229. 
The  light  lines  on  the  pattern  are  called  folding  or  crease 
lines.  The  dotted  lines  on  the  second  figure  are  to  indicate 
extra  material  to  allow  for  lap  in  making  joints. 

1  A  great  many  thin  metal  objects  are  formed  without  seams  by  die-stamp- 
ing or  pressing  a  flat  sheet  into  shape  under  very  heavy  presses.  Examples 
range  from  brass  cartridge  cases  to  steel  wheelbarrows.  Still  another 
division  is  made  by  "spinning,"  as  brass  and  aluminum  ware.  In  stamped 
and  spun  work  the  metal  is  stretched  out  of  its  original  shape,  and  making 
blanks  for  it  depends  upon  much  technical  knowledge  and  experience. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  115 

In  geometry  we  learn  that  a  cylinder  may  be  thought  of  as  a 
prism  with  an  infinite  number  of  sides.  The  development  of 
a  cylinder  then  would  be  a  rectangle  having  a  width  equal  to 


FIGS.  224,>25,[226,  227,  228.— The  five  regular  solids. 


FIG.  229. — A  pattern,  showing  lap. 

the  height  of  the  cylinder  and  a  length  equal  to  the  distance 
around  the  cylinder,  Fig.  230. 

The  length  of  the  pattern  of  a  prism  or  cylinder  is  measured 
on  a  straight  line  called  the  stretchout  line.  This  line  is  the 
stretched  out  length  of  the  shortest  distance  around  the  figure. 
When  the  base  is  perpendicular  to  the  axis  it  will  roll  out  into  a 


116 


MECHANICAL  DRAWING 


straight  line  and  form  the  stretchout.  If  the  prism  or  cylinder 
does  not  have  a  base  perpendicular  to  the  axis,  a  "right  section" 
must  be  taken  in  order  to  get  a  straight  stretchout. 


-  -Stretchout  •=*  Circumference  - 

FIG.  230. — Cylinder  and  pattern. 


124.  Development  of  Prisms. — To  develop  the  prism  of  Fig. 
231  draw  the  stretchout  line  SL  and  on  it  lay  off  1-2,  2-3,  3-4 
and  4-1,  obtained  from  the  top  view.  This  gives  the  length  of 


FIG.  231. — Development  of  a  prism. 

the  stretchout  and  the  true  distances  between  the  vertical  edges. 
At  points  1,  2,  3,  4,  1  on  the  stretchout  draw  vertical  "creases 
lines"  equal  in  length  to  the  corresponding  edges  of  the  prism. 
These  lengths  may  be  easily  projected  across  from  the  front 
view.  The  true  size  of  the  inclined  surface  is  found  by  the 
method  of  auxiliary  projection,  Art.  31,  and  attached  to  one 
of  the  sides  in  its  proper  relation.  The  development  of  the  bot- 
tom may  be  added  if  desired. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   117 

To  develop  the  lateral  surface  of  the  triangular  prism,  Fig. 
232,  draw  the  stretchout  line  SL  and  lay  off  the  distances  1-a, 
a-2,  2-3,  3-6,  6-1,  taken  from  the  top  view.  Points  a  and  6 
do  not  locate  crease  lines  but  are  required  to  find  the  line  of  the 
cut.  Such  extra  " measuring  lines"  are  often  necessary. 


FIG.  232. — Development  of  a  prism. 

125.  Development  of  Cylinders. — Consider  a  cylinder  as  being 
a  many-sided  prism.  To  develop  the  cylinder  of  Fig.  233  assume 
the  position  of  any  convenient  number  of  imaginary  edges.  For 
ease  of  working  these  are  equally  spaced,  which  makes  it  possible 


M  i  Mm;  i  ii  1 1  in  Nun. 

/    £    3    +    f  6     T   0    $    /O  /I    /2  /3  *4  &  /6   / 

FIG.  233. — Development  of  a  cylinder. 

to  obtain  the  length  of  the  stretchout  by  taking  as  many  spaces 
along  SL  as  there  are  spaces  in  the  top  view.  At  each  point  on 
the  stretchout  draw  a  vertical  " measuring  line."  Project  the 
length  of  each  imaginary  edge  across  from  the  front  view  and 
draw  a  smooth  curve  through  the  points. 


118 


MECHANICAL  DRAWING 


Since  the  surface  is  curved,  the  stretchout  as  obtained  is  only 
approximate.  The  more  edges  assumed  the  closer  will  be  the 
approximation,  but  it  is  seldom  necessary  to  have  the  points 
less  than  J^"  apart.  The  accuracy  in  length  of  the  stretchout 
may  be  tested  by  measuring  on  it  the  figured  length  of  the  cir- 
cumference, which  equals  the  diameter  X  3.1416,  or  ird. 


ItlllflUtfKUtfA 


.<iap 


1 

J  i  i  i  1 1 1 1  i  i  1 1 1 1 1 1  u 

/     Z    3    -4-    5    6     7    0    9  /O  //    /2  S3  /<*  &  M    I 


Fia.  234. — Pattern  for  square  elbow. 

126.  To  draw  the  pattern  for  a  two-piece,  or  square,  elbow 
Fig.  234.  This  elbow  consists  of  two  cylinders  cut  off  at  45 
degrees,  so  only  one  need  be  developed.  The  explanation  of  Fig. 
233  applies  to  this  figure  except  that  lap  must  be  allowed  as 
indicated. 


V 


i  i  i  i  i  i  i  I  I  I  i  I  i  I  i  l_ 

FIG.  235. — Square  elbow  pattern,  short  method. 

Sheet-metal  workers  use  short-cut  methods  for  many  problems 
when  laying  out  directly  on  the  metal.  The  square  elbow 
pattern  can  be  constructed  as  in  Fig.  235,  where  a  circle  is  drawn 
with  a  diameter  equal  to  the  diameter  of  the  pipe  and  divided  into 
a  number  of  equal  parts.  These  parts  are  spaced  along  the 
stretchout  £L.  Horizontal  lines  from  the  points  on  the  circle 
and  vertical  lines  from  the  points  on  the  stretchout  will  cross  at 
points  on  the  desired  curve. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   119 

127.  The  development  of  a  four-piece  elbow  is  illustrated  in 
Fig.  236.  To  draw  the  elbow,  first  draw  arcs  having  the  desired 
inner  and  outer  radii  as  shown  at  I.  Divide  the  outer  quarter 
circle  into  six  equal  parts.  Draw  radial  lines  from  points  1,  3 
and  5  to  locate  the  joints.  Draw  tangents  to  the  arcs  at  points 
2  and  4  and  complete  the  figure  as  shown  at  II,  by  tangents  to 
the  inner  quarter-circle.  With  this  view  completed  we  are  ready 
to  start  the  development.  Draw  a  circle  representing  the  cross- 
section  of  the  pipe  (one-half  of  this  view  is  sufficient).  Divide 


Mini 


FIG.  236. — Patterns  for  four-piece  elbow. 

it  into  a  number  of  equal  parts,  and  lay  out  the  stretchout  line 
with  the  same  number  of  equal  parts.  From  the  circle  project 
to  the  elevation  to  locate  the  imaginary  edges.  The  pattern 
for  the  first  section  is  obtained  by  projecting  across  from  the 
elevation  in  the  same  way  as  Fig.  233. 

The  patterns  for  the  four  pieces  may  be  cut  without  waste 
from  a  rectangular  piece  if  the  seams  are  made  alternately  on  the 
inside  or  throat  line  and  outside  line.  To  draw  the  pattern  for 
the  second  section  extend  the  measuring  lines  of  the  first  section 
and  with  the  dividers  take  off  the  lengths  of  the  imaginary  edges 
on  the  front  view,  starting  with  the  longest  one.  The  third  and 


120 


MECHANICAL  DRAWING 


fourth  sections  are  made  in  a  similar  way.     Since  the  curve  is 
the  same  for  all  sections  one  only  need  be  plotted. 

128.  Galvanized  iron  mouldings  and  cornices  are  made  up  of  a 
combination  of  cylinder  and  prism  parts.  A  practical  problem 
in  developments  is  making  the  pattern  for  a  piece  miter ed  to 
"return"  around  a  corner  as  shown  in  the  sketch  of  Fig,  237. 
An  inspection  of  the  figure  shows  the  method  of  working  to  be 
the  same  as  Fig.  233,  the  section  of  the  moulding  taking  the  place 
of  the  top  view  and  having  its  length  laid  out  on  the  stretchout 
line. 


/    3  3        4  s  67 

FIG.  237. — Pattern  for  square  return  miter. 

129.  Development  of  Pyramids  and  Cones. — In  the  case  of 
prisms  and  cylinders  the  stretchout  was  a  straight  line  with  the 
measuring  lines  perpendicular  to  it  and  parallel  to  each  other. 
And  as  their  edges  were  all  parallel  to  the  front  plane  their  true 
lengths  were  always  shown  in  the  front  view.     Pyramids  and 
cones  or  any  objects  larger  at  one  end  than  at  the  other  will  not 
roll  straight,  hence  their  stretchouts  are  not  straight  lines.     Also 
since  they  have  sloping  sides  their  edges  will  not  always  show  in 
their  true  lengths. 

130.  To    find    the    true   length    of  a  line,  revolve  the  line 
until  it  is  parallel  to  one  of  the  planes  of  projection.     Its  pro- 
jection on  that  plane  will  then  be  the  true  length  of  the  line. 
The  pyramid  of  Fig.  238, 1,  is  shown  by  top  and  front  views  at  II. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  121 

The  edge  OA  does  not  show  in  its  true  length  in  either  view. 
However,  if  we  draw  the  pyramid  in  the  position  shown  at  III 
the  true  length  of  OA  is  shown  in  the  front  view.  In  Fig.  Ill 
the  pyramid  has  been  revolved  from  the  position  of  II  about  a 


A' 


FIG.  238. — True  length  of  line. 

vertical  axis  until  the  line  OA  is  parallel  to  the  vertical  plane. 
At  IV  the  line  OA  is  shown  before  and  after  revolving.     Thus 


FIG.  239. — Development  of  a  pyramid. 

the  construction  for  finding  the  true  length  of  a  line  is  as  follows : 
In  the  top  view  with  radius  OA  and  center  0  revolve  the  top 
view  of  OA  until  it  is  horizontal,  project  the  end  of  the  line  down 
to  meet  a  horizontal  line  through  the  front  view  of  A.  Join 
this  point  of  intersection  with  the  front  view  of  0. 

131.  To  draw  the  pattern  for  a  rectangular  pyramid,  Fig.  239. 


122 


MECHANICAL  DRAWING 


Find  the  true  length  of  one  of  the  edges  by  swinging  it  around 
as  shown.  With  this  true  length  as  a  radius  draw  an  arc  of  in- 
definite length  for  a  stretchout  line.  On  this  mark  off  as  chords 


FIG.  240. — Development  of  a  cone. 

the  four  edges  of  the  base  1-2,  2-3,  3-4,  4-1.  Connect 
these  points  with  each  other  in  turn,  and  draw  the  crease  lines  by 
joining  each  point  with  the  center. 


FIG.  241. — Frustum  of  a  cone. 


132.  To  draw  the  pattern  for  a  cone,  Fig.  240.  Consider  a 
cone  as  being  a  many-sided  pyramid  and  assume  the  positions 
of  any  convenient  number  of  imaginary  edges,  using  equal  spac- 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  123 

ing  for  convenience.  With  the  front  view  OA  as  radius  draw  an 
arc  of  indefinite  length  as  a  stretchout.  On  this  step  off  as  many 
points  as  were  assumed  in  the  top  view,  and  at  the  same  distance 
apart.  Connect  beginning  and  ending  points  by  lines  to  the 
center.  The  resulting  sector  is  the  developed  surface. 

If  the  cone  is  cut  off  as  in  Fig.  241  develop  as  before,  then 
with  OC  as  radius  draw  another  arc  between  the  limiting  sides. 

If  the  cone  is  cut  off  at  an  angle  it  will  be  necessary  to  find 
the  true  length  of  every  imaginary  edge  and  lay  it  off  on  the  pat- 
tern, as  shown  in  Fig.  242,  by  revolving  it  around  the  axis  until 
it  is  parallel  to  the  front  plane. 


FIG.  242.— Truncated   cone. 


133.  Development  of  a  Transition  Piece. — A  transition  piece 
is  used  to  connect  a  pipe  of  one  shape  with  another  of  a  different 
shape.  Transition  pieces  are  made  up  of  parts  of  different  kinds 
of  surfaces  and  are  developed  by  triangulation.  The  example 
shown  in  Fig.  243  connects  a  round  pipe  with  a  rectangular  one. 
From  the  picture  it  is  seen  that  this  piece  is  formed  of  four  tri- 
angles, between  which  are  four  conical  parts,  with  apexes  at 
the  corners  of  the  rectangular  opening  and  bases  each  one-quarter 
of  the  round  opening. 

Starting  with  the  cone  whose  apex  is  at  A  divide  its  base  1-5 
into  a  number  of  equal  parts  as  2,  3,  4,  and  draw  the  lines  A-2, 
A-3,  A-4,  giving  triangles  approximating  the  cone.  Find  the 
true  length  of  each  of  these  lines.  This  is  done  in  practical 


124 


MECHANICAL  DRAWING 


DIAGRAM  i 


FIG.  243. — Development  of  transition  piece. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   125 

work  by  constructing  a  separate  diagram,  as  at  I,  knowing  that 
the  true  length  of  each  line  is  the  hypotenuse  of  an  imaginary 
triangle  whose  altitude  is  the  altitude  of  the  cone  and  whose  base 
is  the  length  of  the  top  view  of  the  line. 

On  the  front  view  draw  the  vertical  line  AE  as  the  altitude  of 
the  cone.  On  the  base  EF  lay  off  the  distances  A-l,  A-2, 
etc.  This  is  done  in  the  figure  by  swinging  each  distance  about 
the  point  A  in  the  top  view,  and  dropping  perpendiculars  to  EF. 
Connect  the  points  thus  found  with  the  point  A  in  diagram  I, 
thus  obtaining  the  desired  true  lengths.  Diagram  II,  constructed 
in  the  same  way  gives  the  true  lengths  of  lines  B-5,  B-Q,  etc., 
of  the  cone  whose  apex  is  at  B.  After  the  true  length  diagrams 
are  constructed  start  the  development,  with  the  seam  at  A-l. 
Draw  a  line  a-1  equal  to  the  true  length  of  A-l.  With  1  as 
a  center  and  radius  1-2  taken  from  the  top  view  draw  an  arc. 
Intersect  this  arc  with  an  arc  from  center  a  and  radius  equal  to 
the  true  length  of  A-2,  thus  locating  the  point  2  on  the  develop- 
ment. With  2  as  center  and  radius  2-3  draw  an  arc  and  inter- 
sect it  by  an  arc  with  center  a  and  radius  of  the  true  length  of 
A -3.  Proceed  similarly  with  points  4  and  5  and  draw  a  smooth 
curve  through  the  points  1,  2,  3,  4,  5  thus  found.  Then  attach 
the  true  size  of  the  triangle  A-5-B,  locating  point  B  on  the 
development  by  intersecting  arcs  from  a  with  radius  A-B 
taken  from  the  top  view,  and  from  5  with  radius  the  true  length 
of  B-5.  Continue  until  the  piece  is  completed. 


FIG.  244. — Intersections. 


FIG.  245.— Intersections. 


134.  Intersections. — Whenever  surfaces  come  together  there 
is  said  to  be  a  line  of  intersection.  In  Figs.  244  and  245  a  number 
of  lines  of  intersection  are  shown.  It  is  necessary  for  both  the 
machine  designer  and  the  sheet-metal  worker  to  be  able  to  locate 
a  line  of  intersection  when  one  occurs. 


126 


MECHANICAL  DRAWING 


135.  Intersecting  Prisms. — Several  illustrations  of  intersect- 
ing prisms  are  illustrated  in  Fig.  246. 

To  draw  the  intersection  of  two  prisms,  first  start  the  ortho- 
graphic views.  In  Fig.  247  a  square  prism  passes  through  a  hex- 
agonal prism.  Through  the  front  edge  of  the  square  prism  pass 
a  plane  parallel  to  the  vertical  plane.  The  top  view  of  this  plane 


FIG.  246. — Intersecting  prisms. 

appears  as  a  line  A- A.     The  intersection  of  the  plane  A- A  and 
one  of  the  faces  of  the  vertical  prism  shows  in  the  front  view  as 


8- 


FIG.  247. — Intersection  of  two 
prisms. 


FIG.  248. — Intersection  of  two 
prisms. 


line  a-a,  and  is  crossed  by  the  front  edge  of  the  square  prism, 
at  point  1,  which  is  a  point  on  both  prisms  and  therefore  a  point 
in  the  desired  line  of  intersection.  Plane  B-B  is  parallel  to 
plane  A-A  and  contains  an  edge  of  the  vertical  prism  and  an 
edge  of  the  inclined  prism  which  meet  at  point  2  in  the  front  view. 
Plane  B-B  also  determines  point  3. 

These  planes  are  called  cutting  planes  and  they  may  be  used  for 
the  solution  of  most  problems  in  intersections.  For  intersecting 
prisms  pass  planes  through  all  the  edges  of  both  prisms  within 
the  limits  of  the  line  of  intersection.  Where  the  lines  cut  from 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING   127 

both  prisms  by  the  same  plane  cross  is  a  point  on  the  required 
line  of  intersection.  In  Fig.  248  four  cutting  planes  are  required. 
The  limiting  planes  are  A-A  and  D-D  as  a  plane  in  front  of 
A-A  or  back  of  D-D  would  cut  only  one  of  the  prisms. 

136.  Intersecting  Cylinders. — To  draw  the  line  of  intersection 
of  two  cylinders,  Fig.  249.  Since  there  are  no  edges  on  the  cyl- 
inders it  will  be  necessary  to  assume  positions  for  the  cutting 


Fio.  249. — Intersection  of  two  cylinders. 


planes.  Plane  A-A  contains  the  front  line  of  the  vertical  cylinder 
and  cuts  a  line  from  the  horizontal  cylinder.  Where  these  two 
lines  intersect  in  the  front  view  is  a  point  on  the  required  curve. 
Each  plane  cuts  lines  from  both  cylinders,  which  intersect  at  points 
common  to  both  cylinders.  The  development  of  the  vertical 
cylinder,  obtained  by  the  method  of  Art.  125  is  shown  in  the 
figure. 

The  solution  for  an  inclined  cylinder  is  given  in  Fig.  250  where 
the  positions  of  the  cutting  planes  are  located  by  an  auxiliary 
view.  To  develop  the  inclined  cylinder  the  auxiliary  view  is 
used  to  get  the  length  of  the  stretchout.  If  the  cutting  planes 
have  been  chosen  so  that  the  circumference  of  the  auxiliary  view 
is  divided  into  equal  parts,  the  measuring  lines  will  be  equally 
spaced  along  the  stretchout. 


128 


MECHANICAL  DRAWING 


To  develop  the  portion  of  the  vertical  cylinder  having  the  hole 
for  the  inclined  cylinder,  lay  out  a  portion  of  the  stretchout  and 
project  from  the  front  view  to  the  measuring  lines  as  shown. 


FIG.  250. — Intersection  and  development  of  two  cylinders. 

137.  Intersecting  Cylinders  and  Prisms. — The  intersection 
of  a  cylinder  and  a  prism  is  found  by  the  use  of  cutting  planes  as 
already  described.  In  Fig.  251  a  triangular  prism  intersects  a 


FIG.  251. — Intersection  and  development  of  cylinder  and  prism. 

cylinder.  The  planes  ABCD  cut  lines  from  the  prism  and  lines 
from  the  cylinder  which  cross  in  the  front  view  and  determine 
the  curve  of  intersection  as  shown.  The  development  of  the 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  129 

triangular  prism  is  found  by  taking  the  length  of  the  stretchout 
line  from  the  top  view  and  the  lengths  of  the  measuring  lines 
from  the  front  view.  Since  one  plane  of  the  triangular  prism  is 
perpendicular  to  the  axis  of  the  cylinder,  the  curve  of  intersec- 
tion on  that  face  is  the  radius  of  the  cylinder. 


Fia.  252. — Cylinder   and   cone. 


FIG.  253. — A   cutting   plane. 


138.  Intersection  of  Cylinders  and  Cones. — The  intersection 
of  a  cylinder  and  a  cone  may  be  found  by  passing  planes  parallel 
to  the  horizontal  plane  as  shown  in  Fig.  252.  Each  plane  will 
cut  a  circle  from  the  cone  and  straight  lines  from  the  cylinder. 


FIG.  254. — Cone    and    plane. 

The  straight  lines  of  the  cylinder  cross  the  circle  of  the  cone  in 
the  top  view  at  points  on  the  curve  of  intersection,  which  are 
then  projected  to  the  front  view  as  in  Fig.  253,  where  the  con- 
struction is  shown  for  a  single  plane.  Use  as  many  planes  as  are 
necessary  to  obtain  a  smooth  curve. 

9 


130 


MECHANICAL  DRAWING 


139.  Intersections  of  Planes  and  Curved  Surfaces. — The  line 
of  intersection  of  a  cone  cut  by  a  plane  EE  as  in  Fig.  254,  may 
be  found  by  horizontal  cutting  planes  A,B,C,D.  Each  plane 
cuts  a  circle  from  the  cone,  and  a  straight  line  from  the  plane  EE, 


FIG.  255. — Intersection  of  plane  and  turned  surface. 

thus  locating  points  common  to  both  the  plane  EE  and  the  cone 
as  shown  in  the  top  view.  These  points  when  projected  to  the 
front  view  give  the  curve  of  intersection. 

The  intersection  at  the  end  of  a  connecting  rod  is  found  by 
passing  planes  perpendicular  to  the 
axis,  which  cut  circles  as  shown  in  the 
end  view  of  Fig..  255.  The  points  at 
which  these  circles  cut  the  "flat"  are 
projected  back  as  points  on  the  curve. 
140.  Development  of  Pint  Measure. 
— To  draw  the  development  of  a  pint 
measure,  Fig.  256.  Draw  the  view 
shown  with  the  half  circles  at  top  and 
bottom  in  Fig.  257.  Observe  that  the 
body  is  a  frustum  of  a  cone.  Extend 
the  outline  to  complete  the  cone.  With  MN  as  a  radius  draw 
an  arc.  Step  off  one-half  the  circumference  of  the  base  on  this 
arc  and  draw  the  radial  lines  MK  and  ML.  With  M  as  a 
center  and  MD  as  a  radius  draw  arc  PQ,  completing  the  develop- 
ment of  the  body.  Add  the  necessary  allowance  for  lap. 


FIG.  256. 


GRAPHIC  SOLUTIONS  AND  SHEET-METAL  DRAFTING  131 

To  develop  the  handle  divide  it  into  a  number  of  spaces 
and  step  them  off  on  the  stretch  out  RS.  At  R  lay  off  one- 
half  the  width  of  the  upper  end  of  the  handle  on  each  side 
and  at  S  one-half  the  width  of  the  lower  end  of  the  handle  on 


FIG.  257. — Pattern  for  measure. 

each  side  of  the  stretchout.  Add  allowance  for  laps  and  hems. 
The  true  development  of  the  lip  would  require  the  drawing  of 
lines  through  each  point  and  finding  the  length  of  each  line  as 
described  for  the  truncated  cone,  Fig.  242.  The  usual  practical 
method  is  as  follows,  Fig.  258.  On  a  center  line  oa  draw  an 


132 


MECHANICAL  DRAWING 


arc  with  OA  as  a  radius  and  space  off  one-half  the  circumference 
of  the  top  of  the  body  on  each  side  as  shown  by  dad.  Draw 
the  radii  od.  Increase  OA  by  ac  =  AC  and  increase  od  by  de 
=  DE  as  obtained  from  the  elevation.  Draw  ce  and  the  per- 
pendicular bisector  of  ce  intersecting  the  center  line  at  g.  With 


FIG.  258.— Pattern  for  lip. 

g  as  a  center  and  gc  as  a  radius  draw  arc  ece  to  complete  the 
pattern.     Add  the  necessary  material  for  seams  and  hems. 

141.  Seams  and  Lap. — The  basis  of  sheet-metal  pattern  draft- 
ing is  development.  For  practical  work  it  is  necessary  to  know 
the  processes  of  wiring,  seaming  and  hemming,  and  the  allow- 
ances of  material  to  be  made.  Open  ends  of  articles  are  usually 


FIG.  259. — Wiring,  seaming  and  hemming. 

reinforced  by  enclosing  a  wire  in  the  edge,  as  shown  at  A  in  Fig. 
259.  The  amount  added  to  the  pattern  may  be  taken  as  two 
and  one-half  times  the  diameter  of  the  wire.  Edges  are  also 
stiffened  by  hemming.  Single  and  double  hemmed  edges  are 
shown  at  B  and  C.  Edges  are  fastened  by  soldering  on  lap 
seams,  D,  folded  seams,  E,  or,  the  commonest  way,  by  grooved 
seams,  shown  in  three  stages,  both  inside  and  outside,  at  F. 
An  important  consideration  in  allowing  lap  on  patterns  is  the 
shape  of  the  space  left  at  the  corners  to  prevent  thick  places  in 
the  seam.  This  is  called  notching,  and  is  illlustrated  on  Figs. 
257  and  258. 


PROBLEMS 


133 


CHAPTER  VIII 


PROBLEMS 


142.  The  important  part  of  any  course  in  mechanical  drawing  consists  of  the 
working  of  a  large  number  of  properly  selected  and  graded  problems.  The^probr 
lems  which  follow  are  arranged  somewhat  hi  the  order  of  difficulty  in  each  of  ther 
divisions  of  the  subject.  The  methods  of  presentation  vary  with  the  requirements 
of  the  problems.  Graphic  layouts  are  given  wherever  practicable  as  they  are 
definite  and  save  time  for  both  teacher  and  pupil.  It  is  not  necessary  nor  intended 
that  all  the  problems  be  worked,  but  that  a  selection  be  made  by  the  teacher  to  suit 
his  own  particular  needs.  A  large  number  of  references  to  text  matter  bearing 
upon  the  methods  of  solution  or  principles  involved  are  given  in  connection  with 
the  problems. 

Any  or  all  of  the  drawings  may  be  inked  but  the  best  results  are  generally 
obtained  by  delaying  this  until  the  pupil  has  acquired  the  ability  to  make  a  good 
pencil  drawing. 

One  some  of  the  sheets  it  may  be  found  desirable  to  include  a  freehand  pictorial 
sketch  in  the  style  of  Figs.  308  and  310,  to  indicate  that  the  pupil  has  visualized 
the  object  clearly. 

The  problems  are  designed  for  use  on  the  size  of  sheet  and  layout  given  in 
Fig.  260,  but  it  is  of  course  easily  possible  to  use  other  sizes. 


Fia.  260. — Layout  of  sheet. 
134 


PROBLEMS 


135 


143.  Layout  of  the  Sheet.— Tack  the 
paper  to  the  board  as  described  in  Art.  5. 
The  outside  dimensions  of  the  finished  sheet 
are  11"  X  15"  with  margin  lines  and  record 
strip  as  shown  in  Fig.  260.  The  guide  lines 
for  lettering  the  record  strip  must  be  drawn 
very  lightly.  They  should  not  be  drawn 
until  ready  to  be  used.  On  the  laj^outs  the 
title  for  the^sheet  in  given.  Where  problems 
^Ve  stated  hi  words  the  general  title  of  the 
sheet  is  printed  in  black  face  type.  When 
the  following  method  is  understood  the 

layout  of  the  sheet  should  not  take  more 

than  two  minutes. 


FIG.  261. 


FIG.  262. 


Now  with  T-square  draw  horizontal  lines 
through  horizontal  marks  as  shown  in  Fig. 
262.  Next  draw  vertical  lines  through 
vertical  marks  as  in  Fig.  263.  Then 
brighten  up  the  trim  and  border  lines  and 
the  sheet  will  appear  as  in  Fig.  264,  ready  to 
begin  a  drawing. 

On  the  following  problems  the  figures 
enclosed  in  circles  are  for  locating  the  start- 
ing lines  and  are  always  measured  full  size 
regardless  of  the  scale  of  the  views  of  the 
drawing.  When  such  dimensions  are  given 


The  two  minute  method.  Make  two 
short  vertical  marks  near  the  bottom  of 
sheet,  15"  apart.  Measure  and  mark  %" 
in  from  the  right  hand  end  and  1"  hi  from 
left  hand  end,  Fig  261.  Place  scale  verti- 
cally near  left  edge  of  paper  and  make 
short  horizontal  marks  11"  apart.  Measure 
down  %"  from  top  and  mark.  Measure  up 
%"  from  bottom  and  mark.  From  last 
mark  measure  %"  up  and  mark,  Fig.  261. 


FIG.  263. 


the  lines  which  they  locate  should  be  drawn 
first.  Upon  these  lines  the  drawing  is  built. 
Use  light  full  pencil  lines  and  work  very 
accurately  as  errors  in  starting  often  are 
not  evident  until  the  drawing  is  nearly 
completed. 


FIG.  264. 


136 


MECHANICAL  DRAWING 


Prob.  1.  The  first  sheet,  Fig.  265,  is  a  one-view  drawing  of  a  templet.  The 
complete  specification  would  require  that  the  thickness  of  material  and  kind  of 
material  be  given. 


NAME    OF     SCHOOL 
LOCATION 


(Date; I9_   APPROVED  BY 


FIG.  265.— Prob.  1. 

In  this  and  the  following  three  one-view  problems  the  order  of  making  the 
drawing  in  progressive  stages.  These  stages  should  be  followed  carefully  as  they 
represent  the  draftsman's  practice  as  to  procedure  in  making  drawings. 

It  is  very  necessary  for  the  beginner  to  learn  to  draw  in  good  form,  and  the 
most  important  feature  in  this  regard  is  the  order  of  working.  Do  not  simply 
follow  the  explanations  as  being  directions  for  the  particular  problem,  but  try  to 
understand  the  system  and  the  reasons  for  it.  This  system,  thoroughly  mastered 
at  the  start  will  apply  to  all  drawings  regardless  of  the  number  or  complexity  of 
views  and  will  develop  the  two  requirements  in  execution,  accuracy  and  speed. 


(1)  Lay  out  the  sheet  as  described  in 
Art.  143. 

(2)  Measure   2%"   from   left  border 
line  and  from  this  mark  measure  8%" 
toward  the  right. 

(3)  Lay  the  scale  on  the  paper  verti- 
cally near  the  left  edge,  make  a  mark  2" 
up  and  from  this  measure  53^"   more. 
The  sheet  will  appear  as  in  Fig.  266. 


FIG.  266. 


PROBLEMS 


137 


(4)  Draw  horizontal  lines  i  and  2 
with  the  T-square,  and  vertical  lines  8 
and  4  with  T-square  and  triangle,  Fig. 
267.  These  four  lines  "block  in*'  the 
figure. 


FIG.  267. 


(5)  Between  the  two  vertical  lines 
make  marks  1%"  apart,  and  from 
lowest  line  of  the  figure  measure  two 
distances  vertically,  2>£"  and  !>£"• 
The  sheet  will  appear  as  in  Fig.  268. 


FIG.  268. 


(6)  Draw  the  two  horizontal  lines 
across  the  sheet. 

(7)  Draw    the   vertical  lines,  stop- 
ping   them   on   the   proper   horizontal 
lines,  Fig.  269. 


FIG.  269. 


(8)  Brighten  some  of  the  lines  and 
erase  others  to  obtain  the  finished 
drawing,  Fig.  270. 

Write  your  name,  sheet  number 
and  date  lightly  in  the  record  strip. 
The  record  strip  is  to  be  lettered  in 
after  the  lettering  problems  have  been 
mastered.  Trim  the  sheet  to  finished 
size. 


FIG.  270. 


138 


MECHANICAL  DRAWING 


Prob.  2.  To  make  a  drawing  of  the  stencil,  Fig.  271.  This  drawing  gives 
practice  in  accurate  measuring  with  the  scale,  avnd  making  careful  corners  with 
short  lines. 


NAME    OF    SCHOOL 
LOCATION 


(Date) 


APPROVED  BY 


FIG.  271. 


(1)  Find  the  center  of  the  sheet  inside  the  border  by  laying  the  T-square  blade 
across  the  corners  and  drawing  a  short  piece  of  the  diagonals,  Fig.  272. 

(2)  Through  the  center  draw  a  horizontal  center  line  and  on  it  measure  and  mark 
off  points  for  the  four  vertical  lines,  Fig.  273. 

Draw  the  vertical  lines  lightly  with  T-square  and  triangle.     On  the  first  one 
measure  and  mark  off  points  for  all  horizontal  lines,  Fig.  274. 

(4)  Draw  the  horizontal  lines  as  finished  lines,  and  measure  points  for  the 
stencil  border  lines  on  left  side  and  bottom  as  shown  in  Tig.  275. 

(5)  Draw  border  lines  and  measure  on  them  the  points  for  ties,  Fig.  276. 

(6)  Complete  the  border  by  drawing  the  cross  lines  as  finished  lines  and  bright- 
ening the  other  edges,  Fig.  277. 

(7)  Brighten  the  vertical  lines  and  finish  as  in  Fig.  278. 

(8)  Write  name,  sheet  number  and  date  in  the  record  strip,  and  trim  the  sheet 
to  finished  size. 


PROBLEMS 


139 


\x 

/N 

I 

IG.  275 

• 

FIG.  273. 

_ 

" 

\/ 

\x 

/> 

1 

I 

'IG.  27^ 

t. 

FIG.  275. 

1        II  II        II  II        1 

.  _                                                                           — 

:=                                         - 

\  X 

\/ 

:=                                               - 

.   _            '                                                      '                    *           —1 

1       11  M       1!  II       1 

I 

^IG.  27( 

5. 

FIG.  277. 

acme 

)C= 

3DdDC! 

D 

D 

II 

D 

D 

D 

a 

o 

nczDi: 

nzz 

3DCIZDD 

FIG.  278. 


140 


MECHANICAL  DRAWING 


Prob.  3.  To  make  a  drawing  of  the  shim,  Fig.  279.  When  circles  and  circle 
arcs  occur  on  a  drawing,  their  centers  are  first  located.  The  second  step  is  to 
locate  the  points  of  tangency,  and  make  sure  of  smooth  joints. 


FIG.  279.— Prob. 

Before  starting  this  problem  examine  the  large  compasses  and  bow  pencil. 
Be  sure  that  the  lead  is  carefully  sharpened  and  that  it  is  adjusted  with  the  needle 
point  as  shown  in  Fig.  11,  Art.  10.  Draw  intersecting  lines  on  a  separate  sheet 
and  practice  handling  of  both  instruments  in  drawing  circles,  carefully  observing 
the  operations  illustrated  in  Fig.  12  and  13.  Awkward  manipulation  of  the  com- 
passes is  a  severe  handicap. 

Tangents  occur  constantly  on  all  machine  drawings  and  must  be  drawn 
quickly  and  neatly.  Accuracy  in  setting  the  compasses  to  a  required  radius  should 
be  practiced  as  any  error  is  doubled  when  the  diameter  is  measured.  This  test 
should  be  applied  frequently. 

The  needle  point  may  be  placed  at  the  exact  crossing  of  the  two  centerlines 
by  guiding  it  with  the  little  finger  of  the  left  hand,  resting  the  other  fingers  on 
the  paper.  Art.  Ill  should  be  read  and  the  tangent  arc  and  tangent  line  con- 
structions practiced  until  the  student  is  thoroughly  familiar  with  them. 


FIG.  280. 


PROBLEMS 


141 


(1)  Measure  %"  from  left  border 
and    from    this  mark  measure   2^", 
7",  and  2%'  thus  locating  four  start- 
ing points,  Fig.  281. 

(2)  Measure     vertical     distances. 
Sheet  will  appear  as  in  Fig.  281. 


FIG.  281. 


(3)  Draw  horizontal  and    vertical 
ines  as  in  Fig.  282. 


FIG.  282. 


(4)  Draw  circle  arcs  with  bow 
pencil  (Art.  10).  Be  sure  to  stop  at 
tangent  points,  which  are  located  by 
lines  through  the  centers,  Fig.  280. 
The  sheet  will  appear  as  Fig.  283. 


FIG.  283. 


(5)  Brighten   the   horizontal  lines 
md  finish  as  in  Fig.  284. 

(6)  Write  name,  sheet  number  and 
late  lightly  in  the  record  strip,  and 
brim  the  sheet. 


FIG.  284. 


142 


MECHANICAL  DRAWING 


Prob.  4.  To  make  a  drawing  of  the  shearing  blank,  Fig.  285.  When  a  view 
has  inclined  lines  it  should  first  be  "blocked  in"  with  square  corners.  Angles  of 
30°,  45°  and  60°  are  drawn  with  the  triangles  after  locating  one  end  of  the  inclined 
line. 


OP   SCHOOL  SHEARING   BLANK 

LOCATION  Scale  3"=l'  (DoteJ. 


DRAWN  6Y 

APPROVED  BY. 


FIG.  285.— Prob.  4. 


FIG.  286. 

(1)  Locate  the  vertical  center  line 
and  measure  one-half  of  3'- 9"  on  each 
side,  Fig.  286.  Note  that  this  drawing 
must  be  made  to  the  scale  of  3"  —  I' 
(Art.  13). 


FIG.  287. 

(2)  Locate  vertical  'distances  for  top 
and  bottom  lines. 

(3)  Draw  main  blocking-in  lines  as 
in  Fig.  287. 


PROBLEMS 


143 


FIG.  288. 


FIG.  290. 


FIG.  291. 


FIG.  289. 


(4)  Make  measurements  for  inclined 
lines.     The  drawing  will  appear  as  in  Fig. 
288. 

(5)  Draw   inclined   lines   with   45° 
and  30°-60°  triangles,  Fig.  289. 

(6)  Brighten  lines  and  finish  as  in 
Fig.  290. 

(7)  Write  name,  sheet  number  and 
date  in  the  record  strip,  and  trim  to  size. 


144.  Geometrical  Constructions. — 
The  working  of  a  limited  number  of 
geometrical  exercises  is  valuable  for 
the  practice  in  the  use  of  instruments 
and  to  give  familiarity  with  the  con- 
structions which  occur  most  fre- 
quently. Such  problems  must  be 
worked  very  accurately,  with  a  very 
sharp  pencil  and  comparatively  light 
lines.  A  point  should  be  located  by 
two  intersecting  lines,  and  the  length 
of  a  line  by  two  short  dashes  crossing 
the  given  line. 

The  following  problems  are  for  use 
in  one-quarter  of  the  working  space. 
Lay  out  the  sheet  as  in  Fig.  260  and  draw  horizontal  and  vertical  lines  to  divide 
the  space  into  four  equal  parts,  Fig.  291. 

Prob.  6,  Art.  102,  Fig.  194. — Near  the  center  of  the  space  draw  a  horizontal  line 
3-Ke"  long  and  bisect  it. 

Prob.  6,  Art.  102,  Fig.  194.— Near  the  center  of  the  space  draw  a  vertical  line 
3JiV  long  and  bisect  it. 

Prob.  7,  Art.  103,  Fig.  195. — Above  the  center  of  the  space  draw  a  horizontal 
line  4%  e"  long.     Divide  it  into  five  equal  parts  geometrically. 

Prob.  8,  Art.  103,  Fig.  195.— To  the  left  of  the  center  draw  a  vertical  line  2%" 
long  and  divide  it  into  three  equal  parts  geometrically. 


144  MECHANICAL  DRAWING 

Prob.  9,  Art.  106,  Fig.  201. — Locate  a  point  %"  above  lower  line  of  space  and 
Yz"  from  left  side.  Draw  lines  joining  this  point  with  the  middle  points  of  the 
upper  and  right  hand  sides  of  the  space.  Bisect  the  angle  between  these  lines. 

Prob.  10,  Art.  106,  Fig.  201. — Locate  a  point  %"  below  the  middle  of  the  upper 
line  of  the  space.  Draw  lines  joining  this  point  with  the  lower  right  hand  corner 
and  with  the  middle  of  the  left  side  of  the  space.  Bisect  the  angle  between  these 
lines. 

Prob.  11,  Art.  107,  Fig.  202. — Draw  a  vertical  line  3^"  from  left  edge  of  space. 
From  a  point  on  this  line  %"  below  top  of  space  draw  another  line  making  any 
angle.  Copy  this  angle  so  that  one  side  is  W  from  right  side  of  space  and  vertex 
is  %"  above  bottom  of  space. 

Prob.  12,  Art.  107,  Fig.  202. — From  the  middle  point  of  the  left  side  of  space 
draw  lines  to  upper  and  lower  right  hand  corners.  Copy  this  angle  so  that  one 
side  is  horizontal  and  3^"  above  bottom  of  space. 

Prob.  13,  Art.  108,  Fig.  203. — Draw  a  horizontal  line  4%"  long  and  %"  above 
bottom  of  space.  On  this  line  as  a  base  construct  a  triangle  having  sides  of  3%" 
and  2%". 

Prob.  14,  Art.  108,  Fig.  203.— Draw  a  vertical  line  2%"  long  and  %"  from  left 
side  of  space.  On  it  construct  a  triangle  having  sides  of  4%"  and  434". 

Prob.  15,  Art.  108,  Fig.  206. — Draw  a  horizontal  line  4"  long  and  3£"  above 
bottom  of  space.  Using  this  as  the  longer  of  the  two  sides,  construct  a  right 
triangle  by  the  "6-8-10"  method. 

Prob.  16,  Art.  108,  Fig.  206. — Draw  a  horizontal  line  3%"  long  and  1>£" 
above  bottom  of  space.  Using  this  as  the  hypotenuse,  construct  a  right  triangle 
by  the  "6-8-10"  method. 

Prob.  17,  Art.  109,  Fig.  207. — Draw  a  regular  hexagon  having  a  distance 
across  corners  of  334"- 

Prob.  18,  Art.  110,  Fig.  209. — Draw  a  regular  octagon  having  a  distance  be- 
tween parallel  sides  of  3". 

Prob.  19,  Art.  Ill,  Fig.  210.— Locate  three  points  as  follows:  Point  A  334" 
from  left  edge  of  space  and  3%"  above  bottom  of  space;  B  4%"  from  left  edge 
and  2"  from  bottom;  C  1%"  from  left  edge  and  134"  from  bottom.  Draw  a 
circle  through  A,  B,  and  C. 

Prob.  20,  Art.  113,  Fig.  212.— Locate  a  point  K"  from  bottom  of  space  and  %" 
from  left  edge.  Draw  lines  from  this  point  to  middle  of  top  of  space  and  to  lower 
right  hand  corner.  Draw  an  arc  tangent  to  these  two  lines  with  a  radius  of  \Y^" . 

Prob.  21,  Art.  116,  Fig.  216. — Draw  an  arc  having  a  radius  of  3",  with  its 
center  %"  from  top  of  space  and  Yi"  from  left  edge.  Find  the  length  of  an  arc  of 
60°. 

Prob.  22,  Art.  117,  Fig.  217. — From  the  left  edge  of  the  space  draw  a  horizontal 
line  13^"  long  and  134"  below  top  of  space.  From  right  edge  draw  a  horizontal 
line  13^"  long  and  134"  above  bottom  of  space.  Join  these  two  lines  by  an  "ogee  " 
curve.  Point  E  to  be  one-third  the  distance  from  B  to  C. 

Prob.  23,  Art.  120,  Fig.  221. — Draw  an  ellipse  having  a  major  axis  of  5"  and 
minor  axis  of  23^".  Use  concentric  circle  method. 

Prob.  24,  Art.  120,  Fig.  221. — Draw  an  ellipse  having  a  major  axis  of  6"  and 
a  minor  axis  of  1".  Use  concentric  circle  method. 

Prob.  25,  Art.  121,  Fig.  222. — Draw  an  approximate  ellipse  having  a  major 
axis  of  4J£"  and  a  minor  axis  of  334". 


PROBLEMS  145 

Lettering. — These  exercises  are  for  use  in  one-quarter  of  the  working  space  of  a 
regular  sheet  (see  Fig.  291). 

For  pencil  letters  use  a  long  conical  point.  Rotate  the  pencil  in  the  fingers 
after  each  few  strokes  to  keep  the  point  symmetrical. 

For  ink  letters  use  a  penholder  with  a  cork  grip  and  set  the  pen  well  into  the 
holder.  Always  use  drawing  ink  for  lettering.  To  get  clean  cut  letters  it  is 
necessary  to  wipe  the  pen  frequently  with  a  cloth  penwiper. 

Problems  are  given  for  both  vertical  and  inclined  letters  but  only  one  kind 
should  be  taught  beginners. 

Prob.  26,  Fig.  292. — Single  stroke  vertical  caps.  Lay  out  a  sheet  as  in  Fig.  291. 
Starting  with  the  top  border  line  rule  guide  lines  %"  apart.  With  a  pencil  make  the 
letter  I  on  the  first  line.  Make  each  of  the  other  letters  six  times.  Make  a  careful 
study  of  the  letters  with  the  order  and  direction  of  strokes  as  given  in  Fig.  24. 

Prob.  27,  Fig.  293.— Make  %"  pencil  letters.     Complete  each  line  (Fig.  24). 

Prob.  28,  Fig.  294. — Make  %"  pencil  letters.     Complete  each  line  (Fig.  24). 

Prob.  29,  Fig.  295.  Vertical  Figures. — Make  %"  pencil  figures.  Complete 
each  line. 

Prob.  30,  Fig.  296. — Rule  guide  lines  %*"  apart.  Make  the  first  two  lines  in 
pencil.  Make  the  next  two  lines  very  lightly  in  pencil  and  go  over  them  with  pen 
and  ink.  Use  404  Gillott  pen.  Make  the  fifth  and  sixth  lines  in  ink  without  first 
penciling. 

Prob.  31,  Fig.  297. — Single  stroke  vertical  lower-case.  Starting  one  inch  from 
left  edge  and  one  inch  up,  rule  guide  lines  as  shown.  The  bodies  of  the  letters  are 
y%"  high.  The  first  space  is  %"  up,  the  next  KG",  and  the  next  £{6".  Repeat 
until  there  are  guide  lines  for  eight  lines  of  letters.  Make  pencil  letters  shown  and 
complete  each  line  (Fig.  25). 

Prob.  32,  Fig.  298. — Same  as  Prob.  31,  except  directly  in  ink. 

Prob.  33,  Fig.  299. — Rule  as  for  Prob.  31.  Copy  the  sentences,  first  in  pencil 
and  then  in  ink  as  shown. 

Prob.  34,  Fig.  300. — Single  stroke  inclined  caps.  Lay  out  a  sheet  as  in  Fig.  291. 
Starting  with  the  top  border  line  rule  guide  lines  %"  apart.  With  a  pencil  make 
the  letter  I  on  the  first  line.  Make  each  of  the  other  letters  six  times.  Make  a 
careful  study  of  the  letters  with  the  order  and  direction  of  strokes  as  given  in 
Fig.  30. 

Prob.  36,  Fig.  301.— Make  %"  pencil  letters.     Complete  each  line  (Fig.  30). 

Prob.  36,  Fig.  302.— Make  %"  pencil  letters.     Complete  each  line  (Fig.  30). 

Prob.  37,  Fig.  303. — Inclined  figures.  Rule  guide  lines  %"  apart.  Make  each 
figure  six  times  in  pencil.  On  the  last  line  make  the  fractions  (Fig.  30). 

Prob.  38,  Fig.  304. — Rule  guide  lines  ^ie"  apart.  Make  the  first  two  lines  in 
pencil.  Make  the  next  two  lines  very  lightly  in  pencil  and  go  over  them  with  pen 
and  ink.  Use  404  Gillott  pen.  Make  the  fifth  and  sixth  lines  in  ink  without  first 
penciling. 

Prob.  39,  Fig.  305. — Single  stroke  inclined  lower  case.  Starting  one  inch  from 
left  edge  and  one  inch  up,  rule  guide  lines  as  shown.  The  bodies  of  the  letters  are 
}/%"  high.  The  first  space  is  }/%"  up,  the  next  KG",  and  the  next  £f  6".  Repeat 
until  there  are  guide  lines  for  eight  lines  of  letters.  Make  pencil  letters  shown  and 
complete  each  line  (Fig.  33). 

Prob.  40,  Fig.  306. — Same  as  Prob.  39,  except  directly  in  ink. 

Prob.  40,  Fig.  307. — Rule  as  for  Prob.  39.  Copy  the  sentences  first  in  pencil 
and  then  in  ink  as  shown. 

10         . 


146 


MECHANICAL  DRAWING 


IE  :ET 


z 


HEEEZ I 


FIG.  292.— Prob.  26. 


FIG.  293.— Prob.  27. 


PROBLEMS 


147 


_AIZI._ZZZZIZLE___.ZZZZZ 

flEZZZZZZZI^TZZZZZZZ 
_.....  __— 

_Q ^ j 

tszzzziizzsizzzziz: 
^_L^^.ZI.ESESZSC:REWD.J 

FIG.   294.— Prob.  28. 

ci:::::.::::i.:z 

HZZZZZZ3 

[ISIZZZIIZIE 

t:^zz: 

i 

• 


FIG.  295.— Prob.  29. 


148  MECHANICAL  DRAWING 


i  J;KLM:N:O  P 


^TERTICAL  :  SINGLE.'  STROKE:; 


FIG.  296.— Prob.  30. 


^ 


•::::::::^p-:::::—^ 

,         .  | 

::oS3:ga^ffttes:j 

i 


FIG.  297.— Prob.  31. 


PROBLEMS  149 


aaaaa 

bb 

c 

d 

e 

f 

g 

h 

I 

J 

k 

/ 

m 

n 

0 

P 

q 

r 

s 

t 

u 

V 

w 

X 

y 

z. 

Lower-  case  letters 

a  re  used  for  notes  and  sub -titles. 


FIG.  298.— Prob.  32. 


r 


Words  lettered  In  lower-case  letters 
are  easier  to  read  than  when  made  in 
capitals.  These  letters  are  made  with 
bodies  two-thirds  the  cap  height 


FIG.  299.— Prob.  33. 


150 


MECHANICAL  DRAWING 


..,-    _....        y~— »_«»««*>« -    - -.*-=*-—*•- --,— ,-—    - ••-.= 

1LLT  FTLLh 

._/_.*— .t^^,....J...... /....._/,.  i^-,  L.f.^,jL~~~. 


FIG.  301. — Prob.  35. 


PROBLEMS 


151 


\-'f / 


s: 


: 


! 


:s 


FIQ    302.— Prob.  36. 


5 


FIG.  303.— Prob.  37. 


152 


MECHANICAL  DRAWING 


ABCDEFGHIJKLMNOPQRS 
TUVWX  YZ&  123456  789  O 
ABC  S 

T  O 


INCLINED  SINGLE  STROKE 


FIG.  304.— Prob.  38. 


:r£:±:   rzrfr^f 


FIG.  305.— Prob.  39, 


PROBLEMS  153 


i 

aaaaaa 

bb 

c 

d 

e 

f 

g 

h 

• 

j 

k 

1 

m 

n 

0 

P 

q 

r 

•s 

t 

u 

V 

w 

X 

w 

z 

Lower-c 

,as< 

are  used  for  notes  and  sub-titles 


FIG.  306.— Prob.  40. 


In  making  inclined  letters  there  are 
two  things  to  watch,  first  to  keep  a  uni- 
form slope,  second  to  get  the  rounded 
letters  of  the  correct  shape. 


FIG.  307.— Prob.  41, 


154 


MECHANICAL  DRAWING 


145.  Shape  Description. — Problems  in  the  representation  of  objects  by  views 
are  to  be  drawn  with  the  instruments  and  are  for  the  purpose  of  giving  a  thorough 
understanding  of  the  theory  of  shape  description,  Chap.  III. 

Probs.  42,  43,  44,  45,  Fig.  308.  The  working  space  is  to  be  divided  into  fouri 
equal  spaces,  Fig.  291.  In  each  one  of  the  spaces  draw  three  views  of  the  block 
shown  in  the  picture,  Fig.  308.  The  dimensions  are  given  on  the  partial  views. 
The  student  is  required  to  draw  three  complete  views  of  each  object  and  when  his 
plate  is  completed  it  will  appear  as  in  Fig.  309.  Use  full  size  scale.  Refer  to 
Article  26,  Figs.  46  and  47.  After  completing  the  drawing,  letter  the  record  strip, 
Figs.  260  and  310. 

Probs.  46,  47, 48,  49,  Fig.  310.  Draw  three  complete  views  of  each  of  the  blocks. 
Note  that  each  block  has  an  inclined  surface.  Refer  to  Article  26,  Fig.  48.  Locate 
the  views  as  shown.  Do  not  copy  the  dimensions  or  picture  unless  require/!  by 
your  instructor. 

Prob.  50,  Fig.  311. — The  front  and  side  views  of  a  support  are  shown  and 
located.  Draw  three  complete  views. 

Prob.  51,  Fig.  312. — Given  two  views  of  a  fulcrum.  Draw  three  complete 
views.  First  draw  two  views  of  the  base,  then  draw  the  60°  lines  using  the  30°- 
60°  triangle.  The  height  of  the  fulcrum  is  found  in  the  side  view  where  the  60° 
lines  cross,  and  then  projected  to  the  front  view.  Draw  the  top  view  to  complete 
the  drawing. 

Prob.  52,  Fig.  313. — Given  top  and  front  views  of  a  cast  iron  dovetail.  Draw 
three  complete  views.  In  the  top  view  note  the  center  line  and  lay  off  one-half 
of  1%"  on  each  side  of  it.  Draw  60°  lines  to  intersect  the  %"  depth  line. 

Prob.  53,  Fig.  314. — Draw  three  views  of  the  dovetail  joint  with  the  two  pieces 
together.  Note  the  60°  lines  in  the  top  view. 


L 


KZH 


UQ-J 


«IAME     OF    SCHOOL- 
LOCATION 


SHAPE  DESCRIPTION -BLOCKS 
Full  Size  (Date) I9_ 


DRAWN  BY  " 

APPROVED  BY. 


FIG.  308.— Probs.  42,  43,  44,  45. 


PROBLEMS 


155 


OF   SCHOOL-        I                     SHAPE  DESCRIPTION -BLOCKS  I  DRAWN  BY  HH 

LOCATION  I  Full  Size  (Date; I9_  I  APPROVED  BY. 


Fia.  309. 


•OH 


L 


-m- 


E     OF    SCHOOL 
LOCATION 


SUPPORT  BLOCKS 


(Dote;  __  I9_    APPROVED  BY 


FIG.  310.— Probs.  46,  47,  48,  49. 


156 


MECHANICAL  DRAWING] 


— ®- 


NAME    OF    SCHOOL 


(Date) 19. 


I  DRAWN  BY 
APPROVED  BY_ 


FIG.  311.— Prob.  50. 


NAME     OF    SCHOOL 

LOCATION  Full  Size 


FULCRUM  DRAWN  BY 

(DateJ I9_|  APPROVED  BY_ 


FIG.  312.— Prob.  51. 


PROBLEMS 


157 


— 

-,H 

n 

•> 

H 

jt 

-3 
* 

•H 
« 

; 

f 

—  /* 

-"  —  • 

- 

i 

» 

i 

V,e~ 

—  (jj)  . 

i 

T 

x  * 

& 

r\    , 

s 

^ 

y 

C  1  O 

OVETA 

PRAWN    BV                                             ...       6     EET 

i 

Do 

tc) 

19          APPROVED  BV 

FIG.  313.— Prob.  52. 


H 


,^ 
Kk 
\ 

« 

I 

1 

13 

-  r^  

r  * 

*•  y 

l//ff*v 


NAME     OF"    SCHOOL 

LOCATION  I  Full  Sire 


DOVETAIL   JOINT 

(Date)_ 


I  DRAWN  BY: 
APPROVED  BV. 


— 


FIG.  314.— Prob.  53. 


158 


MECHANICAL  DRAWING 


146.  Placing  Views. — The  location  of  the  views  for  the  preceding  problems  has 
been  given.  When  making  drawings  from  objects  or  for  things  which  have  not  been 
made,  it  is  necessary  for  the  draftsman  to  be  able  to  place  the  views  so  that  they 
will  go  in  the  space  to  advantage.  This  is  done  by  considering  the  space  necessary 
for  each  view  and  comparing  the  total  room  required  with  the  size  of  the  sheet. 


FIG.  315. 

Note  the  object  of  Fig.  315.  The  working  space  in  our  sheet  is  9>£"  X  13%". 
The  top  view  will  require  2"  in  a  vertical  direction  and  the  front  view  3%". 
Allowing  (say)  1"  between  views,  the  total  is  6%".  If  we  subtract  6%"  from 
the  height  of  the  space,  we  have  9K"  less  §%"  =  2%"  to  be  divided  between  top 
and  bottom.  In  Fig.  $16  the  lowest  line  of  the  front  view  has  been  placed  1^" 


r 


A 


JL.I 


f— 1~- 


r~ 


FIG.  316. 


up  which  leaves  1%"  above  the  top  line  of  the  top  view.  Thfe  sum  of  the  hori- 
zontal dimensions  of  the  front  and  side  views  is  8%".  If  we  allow  \W  between 
views  there  is  left  3%"  for  the  two  side  spaces.  In  Fig.  316  the  left  space  is  1%" 
and  the  right  l%".  It  is  not  necessary  to  have  the  spaces_exactly  alike  either 
between  views  or  around  them. 


PROBLEMS 


159 


FIG.  317.— Prob.  54. 


Prob.  54,  Fig.  317. — From  the  picture  of  the  vertical  holding  piece,  draw  three 
(•bmplete  views.  First  work  out  the  placing  of  the  views  as  described  for  Figs.  315 
and  316.  Do  not  dimension  unless  required  by  your  instructor. 

Prob.  55,  Fig.  318. — From  the  picture  and  part  view  of  the  post  cap  draw  two 

views.  Work  out  the  plac- 
ing of  the  views  before 
starting  the^drawing.  Three 
Views  are  ^not  needed  as  two 
of  the  three  would  be  just 
alike. 

Prob.  56,  Fig.  319.— Draw 
three  complete  views  of  the 
bench  hook.  Work  out  the 
placing  of  the  views.  Note 
that  the  end  view  is  to  be 
drawn  by  projecting  from 
the  top  view  instead  of  from 
the  front  view.  This  ar- 
rangement is  sometimes  de- 
sirable, as  in  this  case. 

Prob.    57,    Fig.    320. 

Draw  three  complete  views  of  the  book  rack.  Work  out  the  placing  of  the  views. 
Show  both  ends  in  position  on  the  base  as  the  book  rack  would  appear  when  put 
together.  Scale  6"  =  1'.  Add  dimensions  if  required  by  your  instructor. 


Part  Side  K/e*v 


FIG.  318. — Prob.  55. 


160 


MECHANICAL  DRAWING 


NAME     OF    SCHOOL 
LOCATION 


BENCH  HOOK 


(Oote;_ 


I  DRAWN  BY 
APPROVED  BY_ 


FIG.  319.— Prob.  56. 


NAME     OF"   SCHOOL 
LOCATION 


Scale  6"=l' 


BOOK  RACK 


(Date>_ 


DRAWN  BY  ~ 

APPROVED  BY_ 


FIG.  320.— Prob.  57. 


PROBLEMS 


161 


FIG.  321.— Prob.  58. 

Prob.  68,  Fig.  321. — Draw  top  and  front  views  of  the  nail  box.     Place  views 
carefully.     Draw  full  size. 


FIG.  322.— Prob.  59. 

Prob.  59,  Fig.  322. — Draw  three  complete  views  of  the  step  bracket.     Place 
views  carefully.     Draw  full  size. 
11 


162 


MECHANICAL  DRAWING 


£  Hole  clear  through 


5  Diameter 


FIG.  323.— Prob.  60. 


FIG.  324.— Prob.  61. 


Prob.  60,  Fig.  323. — Draw  two  complete  views  of  the  cast  iron  collar.  Place 
views  as  shown  in  the  layout,  Fig.  325. 

Prob.  61,  Fig.  324. — Draw  two  complete  views  of  the  socket.  Place  views  as 
shown  in  the  layout,  Fig.  325. 


NANNIE     OF   SCHOOL  COLLAR  AND   SOCKET  DETAILS  I  DRAWN  BY: 

LOCATION  Full  Size  (Datej I9_ |  APPROVED  BY, 


FIG.  325. — Layout  for  Probs.  60  and  61. 


163 


See  text 
for  deta/. 


Prob.  62,  Fig.  326. — Draw  two  complete 
views  of  the  centering  plate.  Place  views 
as  shown  in  layout,  Fig.  328. 

Prob.  63,  Fig.  327. — Draw  two  complete 
views  of  bearing.  Place  views  as  shown  in 
layout,  Fig.  328. 


Diameter 


FIG.  327.— Prob.  63. 


CENTERING  PLATE  AND   BEARING  DRAWN  BY 

FUII  Size  (Date) I9_   APPROVED  BV_ 


FIG.  328.— Layout  for  Probs.  62  and  63. 


164 


MECHANICAL  DRAWING 


FIG.  329.— Prob.  64. 

Prob.  64,  Fig.  329. — Draw  three  complete  views  of  the  horizontal  guide.     Lo- 
cate views  as  shown  in  layout,  Fig.  330.     Add  dimensions  if  required  by  instructor. 


NAME     OF    SCHOOL  HORIZONTAL   GUIDE 

LOCATION  Full  Size  (Dote) 


FIG.  330.— Layout  for  Prob.  64. 


PROBLEMS 


165 


FIG.  331.— Prob.  65. 


Prob.  65,  Fig.  331. — Draw  three  complete  views  of  the  bird  feeding  stick. 
Work  out  the  placing  of  the  views  as  for  Figs.  315  and  316.  Draw  full  size. 
After  blocking  in  the  three  views,  measure  the  depth  of  the  holes  on  the  top  and 
side  views.  Then  draw  the  holes  in  the  front  view  and  project  to  the  top  and 
side  views.  Show  center  lines  for  the  holes. 

147.  Sections. — As  explained  in  Article  30,  a  sectional  view  shows  an  object  as 
if  it  had  been  cut  and  a  part  removed.  The  cut  surface  is  indicated  by  section 
lining  with  a  fine  line,  generally  at  45°,  spaced  uniformly.  The  spacing  is  done 
entirely  by  eye.  In  the  following  figures  use  the  spacing  of  the  first  rectangle  of 
Fig.  159. 

Prob.  66,  Fig.  332. — The  layout  for  problem  66  is  shown  as  a  freehand  sketch. 
The  student  is  required  to  make  a  mechanical  drawing  of  the  cylindrical  spacer. 
The  right-hand  view  is  to  be  drawn  as  a  section,  Art.  30. 

Prob.  67,  Fig.  333. — The  sketch  layout  for  a  clamping  disc  is  shown  in  the 
figure.  Make  a  mechanical  drawing.  The  right  view  is  to  be  in  section. 

Prob.  68,  Fig.  334. — The  sketch  layout  for  a  cast  iron  piston  body  is  shown  in 
the  figure.  Make  a  mechanical  drawing  showing  the  left  view  in  section. 

Prob.  69,  Fig.  335. — The  sketch  layout  of  a  protected  bearing  is  shown  in  the 
figure.  Make  a  mechanical  drawing  showing  the  right  view  as  a  half  section, 
Art.  30,  Fig.  73, 

Prob.  70,  Fig.  336. — Draw  three  views  of  the  yoke,  the  front  view  to  be  a  sec- 
tion. Note  that  there  are  two  pieces,  the  yoke  and  the  bushing.  Read  Article 
30  in  regard  to  section  lines  when  two  pieces  are  drawn  together,  Fig.  74. 


166 


MECHANICAL  DRAWING 


FIG.  332.— Prob.  66. 


© 


NAME     OF    SCHOOL. 
LOCATION 


CLAMPING   DISC 

(Date;. 


DRAWN  BY 

19 APPROVED  BY. 


FIG.  333.— Prob.  67. 


PROBLEMS 


167 


/ 

- 

- 

r 

_ 

i 

[  i 

i 

..V! 



_Tfc 

L, 

i 
i 

i 

t 



JL_ 

! 



i 

-- 

H 

i  
i 

<r- 

1 

| 

i  s. 

*I 

-*i*- 

1 

•/ 

*|*  e* 

1 

I 

D 

V.. 

—  J 

,J 

NAIV1E     OF    SCHOOL 

LOCATION  |  Full  Size 


PI3TON   BODY 


(Date;. 


DRAWN  BY 

j_    APPROVED  BY_ 


FIG.  334.— Prob.  68. 


JAME     OF    SCHOOL"                                     PROTECTED    BEARING  DRAWN  BY  = 

LOCATION  Full  Size  (Date) I9_    APPROVED  BY. 


FIG.  335.— Prob.  69. 


168 


MECHANICAL  DRAWING 


NAME     OF  SCHOOL.        I  YOKE  I  DRAWN  BY 

LOCATION  |    Full  Size  (Date) I9_|  APPROVED  BY_ 


FIG.  336.— Prob.  70. 


148.  Auxiliary  Views. — Center  or  other  reference  lines  are  used  in  working 
problems  in  auxiliary  projection.  See  Arts.  31  and  32. 

Prob.  71,  Fig.  337. — The  figure  gives  the  layout  for  two  problems.  Draw  the 
top,  front  and  the  complete  auxiliary  view  of  the  rectangular  prism  as  shown. 

Prob.  72,  Fig.  337.  Draw  the  two  views  given  and  the  complete  auxiliary 
view  of  the  square  prism. 

Prob.  73,  Fig.  338. — The  figure  gives  the  layout  for  two  problems.  Draw  the 
views  given  and  the  complete  auxiliary  view  for  the  dovetail  moulding. 

Prob.  74,  Fig.  338. — Draw  the  two  views  given  and  the  complete  auxiliary 
view  of  the  "half  round." 

Prob.  75,  Fig.  339. — A  picture  and  layout  for  an  angle  stop  are  shown  in  the 
figure.  Draw  the  two  views  given  and  a  part  auxiliary  view.  The  picture  need 
not  be  copied.  Dimension  if  required  by  instructor.  This  is  the  form  in  which 
auxiliary  projection  most  frequently  occurs  in  practical  work,  Art.  31,  Fig.  80. 

Probs.  76,  77,  78,  79,  80,  81,  Figs.  340  to  345. — Choice  of  any  two  of  these 
problems  will  require  the  same  space  as  problems  71  and  72.  Draw  the  two  views 
given  and  the  complete  auxiliary  view  on  the  center  line  indicated. 

Prob.  82,  Fig.  346. — The  figure  gives  the  layout  and  picture  of  a  hollow  mould- 
ing. Draw  the  two  views  given,  and  from  these  draw  the  complete  auxiliary 
view. 


PROBLEMS 


169 


NAME      OF    SCHOOL 
LOCATION 


AUXILIARY     PROJECTION  DRAWN  BY 

3  (Date) 19_ 


FIG.  337.— Probs.  71  and  72. 


OF  SCHOOL  AUXILIARY    PROJECTION 

LOCATION  Full  Size  (Date)- 


FIG.  338.— Probs.  73  and  74. 


170 


MECHANICAL  DRAWING 


NAME     OF    SCHOOL  ANGLE    STOP  DRAWN  BY 

LOCATION  Full  Size  (Date) I9_     APPROVED  BY 


FIG.  339.— Prob.  75. 


r 


(3 


I 


FIQ.  340.—  Prob.  76.  FIG.  341.— Prob.  77.  FIG.  342.— Prob.  78. 


PROBLEMS 


171 


FIG.  343.— Prob.  79.         FIG.  344.— Prob.  80. 


FIG.  345.— Prob.  81. 


NAME     OF    SCHOOL                                       AUXILIARY   PROJECTION  DRAWN  BY r^— 

LOCATION  Full  Size  (Date) 19 APPROVED  BY _ 


FIG.  346.— Prob.  82. 


172 


MECHANICAL  DRAWING 


NAME      OF    SCHOOL  REVOLUTION 

LOCATION  Full  Size  (Date; I9_ 


DRAWN  BY : 
APPROVED  BY_ 


FIG.  347.— Prob.  83. 


.NAME    OF     SCHOOL 
LOCATION 


REVOLUTION 


(Date; »_ 


DRAWN  BY 

APPROVED  BY_ 


FIG.  348.— Prob.  84. 


PROBLEMS 


173 


148.  Revolutions. — Prob.  83,  Fig.  347. — The  figure  shows  the  completed  prob- 
lem. This  should  not  be  copied  but  is  given  for  comparison.  The  sheet  is  divided 
into  four  spaces  as  shown.  The  first  space  is  for  three  views  of  the  object.  In 
space  No.  2  (upper  right  hand)  the  object  is  shown  after  being  revolved  from  the 
position  of  space  No.  1,  through  45°,  about  an  axis  perpendicular  to  the  vertical 
plane. 

The  front  view  was  drawn  first  and  the  top  and  side  views  obtained  by  pro- 
jection. In  space  No.  3  (lower  left  hand)  the  object  is  shown  after  being  revolved 
from  position  No.  1  through  30°  about  an  axis  perpendicular  to  the  horizontal 
plane.  In  space  No.  4  the  object  has  been  revolved  from  position  No.  2  through 
30°  about  an  axis  perpendicular  to  the  side  plane  (Art.  33).  Problem  84  is  to  be 
worked  in  the  same  way,  using  the  dimensions  given. 

Prob.  84,  Fig.  348. — From  the  given  views  draw  three  complete  views  of  the 
object  in  the  position  indicated  in  each  space.  Read  explanation  of  Problem  83. 

Probs.  85  to  90,  Fig.  349. — These  figures  are  given  as  alternates  for  problem  84. 
Draw  three  views  of  the  one  selected,  and  revolve  using  the  same  positions  and 
placing  as  in  Fig.  348. 


Prob.  85.  Prob.  86.  Prob.  87.  Prob.  83.         Prob.  89.     Prob.  90.] 

FIG.  349.— Probs.  85  to  90. 


174 


MECHANICAL  DRAWING 


ISOMETRIC  DRAWING 
Full  Size  (Date)_ 


DRAWN  BV 

_/9_  APPROVED  SV_ 


FIG.  351.— Probs  91  and  92. 


.1 


- 


NAME     OF    SCHOOL 
LOCATION 


ISOMETRIC  DRAWING 

(Date). 


DRAWN  BY 

_I9_    APPROVED  BV_ 


FIG.  352.— Probs.  93  and  94. 


PROBLEMS  175 

149.  Pictorial  Drawing. — When  making  isometric  drawings  it  is  necessary  to 
decide  upon  the  point  which  will  be  taken  for  the  center  of  the  three  axes.  The 
sometric  cube  with  the  two  starting  positions  for  the  axes  is  shown  in  Fig.  350. 
rhe  position  to  use  is  given  on  the  layout  for  each  of  the  following  problems. 
Remember  that  all  measurements  must  be  taken  parallel  to  the  axes  (Arts  34  to 
40). 

Prob.  91,  Fig.  351.— Draw  the  orthographic  views  as  given  for  the  block. 
Construct  the  isometric  drawing  using  the  axes  in  the  second  position  as  started 
on  the  layout.     The  heavy  lines  indicate  the  corner  of  the  object  from  which  the 
axes  start  (Art.  35). 

Prob.  92,  Fig.  351. — Draw  the  given  views  and  an  isometric  drawing  of  the 
lalf  lap  joint  (Art.  35). 

Prob.  93,  Fig.  352. — Draw  the  views 
riven  and  an  isometric  drawing  of  the  tenon. 
Prob.  94,  Fig.  352. — Draw  views  given 
and  an  isometric  drawing  of  the  mortise. 

Prob.  95,  Fig.  353. — Make  an  isometric 
Irawing  of  the  notched  block.  Locate  as  on 
?ig.  355.  Start  with  the  corner  indicated 
>y  heavy  lines. 

Prob.  96,  Fig.  354. — Make  an  isometric  FIG.  350. 

Irawing  of  the  plate.     Locate  as  on  Fig.  355. 

Prob.  97,  Fig.  356. — Make  an  isometric  drawing  of  the  stirrup.     The  drawing 
is  started  on  the  layout,  of  Fig.  358.     Note  the  heavy  lines  at  the  starting  corner. 
The  slant  lines  of  Fig.  356  are  non-isometric  lines  (Art.  36). 

Prob.  98,  Fig.  357. — Make  an  isometric  drawing  of  the  brace.     The  drawing 
is  started  in  Fig.  358.     Note  the  60°  angle  and  read  Art.  37  before  making  the 
[rawing. 

Prob.  99,  Fig.  359. — Make  an  isometric  drawing  of  a  cube  each  edge  of  which 
measures  3".  On  each  face  construct  an  isometric  circle  by  method  of  Art.  38. 

Prob.  100,  Fig.  359. — Make  an  isometric  drawing  of  a  cylinder  2^"  diameter 
and  3^"  high?  resting  on  a  square  plate  as  shown.  First  draw  the  square  plate. 
)n  it  construct  a  square  prism  having  sides  of  2^2"  and  a  height  of  3}^".  On  the 
;op  and  bottom  faces  of  the  prism  construct  isometric  circles.  Vertical  tangent 
ines  will  complete  the  drawing.  Note  that  the  distance  between  these  vertical 
ines  is  more  than  the  actual  diameter  of  the  cylinder.  Why? 

Prob.  101,  Fig.  360. — Draw  the  three  views  given  of  the  hung  bearing  and  make 
an  isometric  drawing.  Most  of .  the  construction  is  indicated  on  the  layout. 
Vlake  the  drawing  as  though  all  corners  were  square  and  then  construct  the  curves 
[Art.  38). 

Prob.  102,  Fig.  361. — Make  an  isometric  drawing  in  section  of  the  post  socket. 
Locate  as  on  Fig.  363  (Art.  33,  Fig.  95). 

Prob.  103,  Fig.  362. — Make  an  isometric  drawing  as  a  half  section  of  the  box. 
Locate  as  on  Fig.  363  (Art.  39,  Fig.  94). 


176 


MECHANICAL  DRAWING 


T 


1 


K- 

?r 


FIG.  353.— Prob.^QS. 


FIG.  354.— Prob.r96. 


JAME     OF    SCHOOL. 
LOCATION 


ISOMETRIC  DRAWING 

(DoteJ. 


DRAWN  BY  ZZH 
19  _    APPROVED  BV_ 


FIG.  355.— Layout  for  Probs.  95  and  96. 


PROBLEMS 


177 


FIG.  356. — Prob.  97. 


3f 

FIG.  357.— Prob.  98. 


NAME     OF    SCHOOL  ISOMETRIC   DRAWING 

LOCATION  Full  5ize  (Oote.L 


DRAWN  BY 

_  (9 APPROVED   BY 


FIG.  358. — Layout  for  Probs.  97  and  98. 


12 


178 


MECHANICAL  DRAWING 


NUMV1E     OF    SCHOOL 
LOCATION 


ISOMETRIC   CIRCLES  DRAWN  BY  rZ 

Full  S\ze  (Date)  ___  I9_    APPROVED  BY_ 


FIG.  359.— Probs.  99  and  100. 


FIG.  360.— Prob.  101. 


PROBLEMS 


179 


~i 


"5 


FIG.  361.— Prob.  102. 


FIG.  362.— Prob.  103. 


NAN/IE     OF   SCHOOL 
LOCATION 


ISOMETRIC    SECTIONS 
Full  Size  (Cta*eL 


FIG.  363.— Layout  for  Probs.  102  and  103. 


180 


MECHANICAL  DRAWING 


FIG.-  364.— Prob.  104. 


FIG.  365.— Prob.  105. 


Prob.  104,  Fig.  364. — Make  an  oblique  drawing  of  the  angle  using  layout  of 
Fig.  366  (Arts.  42  to  44). 

Prob.  105,  Fig.  365. — Make  an  oblique  drawing  of  the  crank. 
Prob.  106,  Fig.  367. — Make  an  oblique  drawing  of  the  clock  case. 


~ @~ 


® * 


4AVIE     OF   SCHOOL- 
LOCATION 


OBLIQUE  DRAWING 

(Date;. 


DRAWN  BY 

.  _I9_  APPROVED  BY. 


FIG.  366. — Layout  for  Probs.  104  and  105. 


PROBLEMS 


181 


FIG.  367.— Prob.  106. 


Prob.  107. — Make  a  cabinet  drawing  of  the  bird  feeding  stick  (Fig.  331). 

Probs.  108  to  115,  Fig.  370. — Make  freehand  pictorial  sketches  of  the  objects 
shown,  in  any  of  the  methods  studied.  Problem  108  is  illustrated  in  Fig.  368  as 
it  would  appear  when  sketched  in  isometric  and  oblique  drawing.  The  same  problem 
is  shown  in  Fig.  369  as  a  single  figure  on  one  sheet  sketched  in  angular  perspective. 
This  sheet  illustrates  in  general  such  assignments  as  may  be  made  in  pictorial 
sketching  from  actual  parts  of  machines  or  other  objects. 

As  described  in  Arts.  46  and  47  a  perspective  sketch  is  drawn  from  the  object 
by  estimating  the  directions  of  lines  and  proportions  of  lengths  by  observation, 
testing  with  the  pencil  as  the  sketch  proceeds. 

To  make  a  sketch  in  angular  perspective  when  the  orthographic  views  are  given 
instead  of  the  object  itself,  the  plan  is  first  drawn  with  its  front  corner  against 
a  line  representing  the  picture  plane,  as  shown  in  Fig.  369.  A  point  S  in  front  of 
this  corner  is  taken  as  the  "station  point"  of  the  observer.  Lines  drawn  from  this 
point  to  each  point  on  the  object  cross  the  line  of  the  picture  plane  and  give  the 
widths  of  the  picture.  From  S  lines  drawn  parallel  to  the  lines  of  the  plan  give 
the  vanishing  points  V  and  V.  The  line  V-V  then  becomes  the  horizon.  Below 
the  horizon  draw  the  horizontal  line  G.L.  called  the  ground  line.  At  the  intersec- 
tion of  G.L.  and  a  perpendicular  from  the  front  corner  of  the  plan,  draw  a  vertical 
line  representing  the  front  edge  of  the  object.  Vertical  measurements  are  all  made 
on  this  line.  A  study  of  Fig.  369  will  show  the  method  of  making  the  sketch  by 
vanishing  the  horizontal  lines  to  their  vanishing  points  and  dropping  perpendiculars 
from  the  picture  plane  to  locate  the  widths. 


182 


MECHANICAL  DRAWING 


FIG.  368. — Solution  of  Prob.  108  in  isometric  and  oblique. 
/" 

4*. 


FIG.  369.— Solution  of  Prob.  108  in  Perspective. 


PROBLEMS 


C 


FIG.  370.— Probs.  108  to  115. 


184 


MECHANICAL  DRAWING 


150.  Size  Description. — Size  description  or  dimensioning  is  a  very  important 
part  of  mechanical  drawing.  The  principles  of  Chapter  IV  should  be  applied 
to  the  solutions  of  the  following  problems. 

Prob.  116,  Fig.  371. — Three  partial  views  of  a  slide  rod  carrier  are  given. 
Make  a  complete  working  drawing  with  all  necessary  dimensions  (Art.  49). 

Prob.  117,  Fig.  372. — Make  a  complete  three  view  working  drawing  of  the 
adjustable  center.  Locate  the  views  carefully  (Art.  146). 

Prob.  118,  Fig.  373. — Make  working  drawings  of  the  gland  and  bearing  with 
complete  dimensions.  The  diameter  of  the  hole  (1")  and  of  the  hub  (!%") 
should  be  added  to  the  gland.  For  the  bearing  the  distance  from  the  under  side  of 
base  up  to  center  of  hole  is  2".  The  length  of  the  hole  is  1%",  and  the  diameter  of 
the  hole  is  %". 

Prob.  119,  Fig.  374. — The  figure  is  drawn  half  size.  Make  a  full  size  working 
drawing  and  dimension  completely.  Either  the  dividers  or  the  scale  can  be  used 
to  transfer  the  views  to  the  student's  drawing.  Obtain  dimensions  by  scaling 
your  drawing. 


Prob.  120,  Fig.  375. — Copy  the  views  double  size, 
views.     Obtain  dimensions  by  scaling  your  drawing. 


Completely  dimension  the 


J-     L_  >• 


_i 


h- 


Nfi 


NXXA/1E     OF    SCHOOL- 
LOCATION 


SLIDE  ROD  CARRIER 

(Dote;. 


DhAWN  BV  

APPROVED  BY. 


FIG.  371.— Prob.  116. 


PROBLEMS 


185 


NAME     OF     SCHOOL 
LOCATION 


ADJUSTABLE      CENTER 


(Dare) i9_ 


ORA*VN  BV  rrz; 

APPROVEP  6Y_ 


FIG.  372.— Prob.  117. 


text  for  missing  dirheratonsf 


NAME     OF    SCHOOL  DIMENSIONING    STUDIES  I  DRAWN  BY 

LOCATION  Full  Size  (Date)  19      APPROVED  BY_ 


FIG.  373.— Prob.  118. 


186 


MECHANICAL  DRAWING 


I 

f 

I 
I 

I 


FIG.  374.— Prob.  119. 


PROBLEMS 


187 


FIG.  375.— Prob.  120. 


188 


MECHANICAL  DRAWING 


Prob.  121,  Fig.  376. — Make  a  complete  working  drawing  of  the  lever.  Give  all 
dimensions.  Do  not  copy  notes  nor  locations  from  the  picture.  The  student 
is  required  to  draw  dimension  and  extension  lines.  Fig.  377  is  the  layout  for  this 
problem. 


6J  Center  to  Center 

FIG.  376.— Prob.  121. 


FIG.  377. — Layout  for  Prob.  121. 


•  PROBLEMS 


189 


Diam.  of  hub     I 
.        .  hole      j 


Prob.  122,  Fig.  378.— Make  a 
complete  working  drawing  of  the  bell 
crank.  Give  all  dimensions.  Do  not 
copy  the  notes  from  the  picture.  Fig. 
379  is  the  layout. 


Length 

of  hub  ij 


FIG.  378.— Prob.  122. 


NAME     OP    SCHOOL 
LOCATION 


BELL    CRANK 


_I9_|  APPROVED  BY. 


FIG.  379.— Layout  for  Prob.  122. 


190 


MECHANICAL  DRAWING 


[See  text  for  instructions] 


NAME     OF  SCHOOL 

LOCATION  Half  Size 


(Datej  __  I9^_ 


APPROVED  BV_ 


FIG.  380.— Prob.  123. 


FIG.  381. — Prob.  124. 


PROBLEMS 


191 


FIG.  382.— Prob.  125. 


Prob.  123,  Fig.  380. — Draw  the  two  views  of  the  rail,  and  locate  dimensions 
carefully.     Scale  6"  =  1'.     The  distances  are  as  follows: 
Stock  is  1%"  X  6"  X  22". 
Distance  from  A  to  B  is  19%". 
Distance  from  C  to  D  is  %". 
Distance  from  E  to  F  is  I". 

Prob.  124,  Fig.  381. — Draw  two  views  of  the  saw  horse,  and  completely  dimen- 
sion.    Scale  3"  =  1'. 

Prob.   125,   Fig.   382. — Make  a  complete  working  drawing  at  the   support. 
Choose  views  and  locate  carefully  (Art.  86). 


192 


MECHANICAL  DRAWING 


Stretchout 


NAME    OF     SCHOOL.                                                DEVELOPMENT  DRAWN  BY  —_ 

LOCATION  Full  Size  (Date) |9__    APPROVED  BY 


FIG.  383.— Prob.  126. 

Prob.  126,  Fig.   383. — Develop  the  lateral  surface  of  the  truncated  square 
prism.     Use  the  given  stretchout  (Art.  124). 

Probs.  127  to  130,  Figs.*384*to'387.— Developjthejlateral  surface. 


384 


\ 


60'  60* 


385  386 

FIGS.  384  to  387.— Probs.  127  to  130. 


387 


J 


PROBLEMS 


193 


Stretchout 


— <D 


NAME    OF   SCHOOL  DEVELOPMENT 

LOCATION  Full  Sire 


DRAWN  BV=T 
APPROVED  BY 


FIG.  388.— Prob.  131. 


Prob.  131,  Fig.  388. — Develop  the  lateral  surface  of  the  cylinder.     Use  the 
given  stretchout  (Arts.  125  and  126). 

Probs.  132  to  135,  Figs.  389  to  392. — Develop  the  surfaces. 


389 


390  391 

FIGS.  389  to  392.— Probs.  132  to  135. 


392 


13 


194 


MECHANICAL  DRAWING 


4AIV1E     OF    SCHOOL 
LOCATION 


DEVELOPMENT 


(Dote; I 


DRAWN  BY  

APPROVED  BY_ 


FIG.  393.— Prob.  136. 

Prob.  136,  Fig.  393. — Develop  the  truncated  rectangular  pyramid.  First 
revolve  edge  04  until  its  true  length  shows  in  the  front  view.  Start  with  this  edge 
in  the  position  shown  to  the  right  of  the  views  (Arts.  129  and  130). 

Probs.  137,  138,  139,  Figs.  394,  395,  396.— Develop  the  slanting  surfaces. 


*.-  '  ,:^.4.'~ 

FIG.  394.— Prob.  137.  FIG.  395.— Prob.  138  FIG,  396.— Prob.  139. 


PROBLEMS 


195 


NAME     OF    SCHOOL  DEVELOPMENT 

LOCATION  Full  Size  (Dote)_ 


DRAWN   BY    "3IZ 
APPROVED  BT 


FIG.  397.— Prob.  140. 


Prob.  140,  Fig.  397. — Develop  the  lateral  surface  of  the  frustum  of  the  cone 
(Art.  132). 

Probs.  141,  142,  143,  Figs.  398,  399,  400. — Develop  the  lateral  surfaces  of  the 
parts  of  cones. 


FIG.  398.— Prob.  141.  FIG.  399.— Prob,  142.  Fio.  400.— Prob.  143. 


196 


MECHANICAL  DRAWING 


Center  line  for 
,    development  of 
i     (Width  o  f  handle  I      one  ha/f 


Width  of  handle  * 


\~ — 3  "Di* 


Center  line  for  handle 


./IE     OF    SCHOOL 
LOCATION  Full  Sire 


PATTERN   FOR   MEASURE 


(Date; 19  _ 


DRAWN  BY 

APPROVED  BY 


FIG.  401.— Prob.  144. 


Prob.  144,  Fig.  401. — Make  a  complete  development  of  the  pint  measure  (Arts. 
140  and  141). 


FIG.  403.—  Prob.  146. 


FIG.  402.—  Prob.  145. 

Prob.  145,  Fig.  402.  —  Make  a  complete  development  of  the_funnel. 
Prob.  146,  Fig.  403.  —  Make  a  complete  development  of  the  scoop. 


PROBLEMS 


197 


Find  lines  of  intersection . 


L_3 


t 


NAIVIE      OF   SCHOOL 


INTERSECTIONS 


(Date) 19 APPROVED  BY 


FIG.  404.— Probs.  147  and  148  (Art.  135). 


f/nc/  lines  of  infersec  tion 


NAME     OF    SCHOOL-  INTERSECTIONS  DRAWN  &f 

LOCATION  Full  Size  (Date; I9_    APPROVED  BY_ 


FIG.  405.— Probs.  149  and  150  (Art.  136). 


198 


MECHANICAL  DRAWING 


N/MVIE     OF    SCHOOL-  INTERSECTIONS  DRAWN  BY 

LOCATION  full  Size  (Date) _  I9_    APPROVED  BY 


FIG.  406.— Probs.  151  and  152  (Art.  137). 


Find  line  of  intersection  and  develop  cylinder 


4AME     OF    SCHOOL  DEVELOPMENT 

LOCATION  Full  Size  (Date) I 


DRAWN  BY  

> I  APPROVED  BY_ 


FIG.  407.— Prob.  153. 


PROBLEMS 


199 


FIG.  408.— Prob.  154.  FIG.  409.— Prob.  155.  FIG.  410.— Prob.  156. 


Prob.  164,  Fig.  408. — Find  line  of  intersection  and  develop  lateral  surface  of 
the  pyramid. 

Prob.  155,  Fig.  409. — Find  line  of  intersection  and  develop  lateral  surface  of 
the  pyramid. 

Prob.  156,  Fig.  410. — Find  line  of  intersection  and  develop  lateral  surface  of  cone. 
Any  of  the  intersection  problems  may  be  used  for  development  by  solving  one 
problem  on  a  sheet. 


200 


MECHANICAL  DRAWING 


k//— J 


True  fength  diagram 
here 


NAME     OF    SCHOOL       I                                 TRANSITION   PIECE  DRAWN  BV  = 

LOCATION  |  Full  Size  (Date; I9_J  APPROVED  BY_ 


Fia.  411.— Prob.  157. 


Prob.  157,  Fig.  411. — Develop  the  surface  of  the  transition  piece  (Art.  133). 
Probs.  158,  159,  160.— Figs.  412,  413,  414.     Develop  surface  of  transition 


pieces. 


FIG.  412.— Prob.  158,  Fia.  413.— Prob.  159. 


FIG.  414.— Prob.  160. 


PROBLEMS 


201 


152.  Screw  threads  and  bolts. — It  is  very  necessary  for  a  draftsman  to  know 
the  forms  of  screw  threads  and  the  conventional  methods  of  drawing  bolts  and 
screws.  Threads  are  always  understood  to  be  single  and  right  hand  unless  other- 
wise specified.  A  right  hand  thread  enters  when  turned  clockwise.  A  left  hand 
thread  enters  when  turned  counter  clockwise,  and  is  always  marked  "L.H."  on  a 
drawing. 

Prob.  161,  Fig.  415. — In  the  left  half  of  the  sheet  construct  two  complete  turns  of 
a  right  hand  helix  whose  diameter  is  4"  and  pitch  1%"  (Arts.  70  and  71).  In 
the  right  half  of  the  sheet  draw,  as  shown  in  the  layout,  the  forms  of  the  V  thread, 
U.  S.  Std.  thread  and  square  thread.  Pitch  l"(Art.  70).  Letter  the  name  of 
each  form  under  the  drawing  of  it. 

Prob.  162. — In  the  left  half  of  the  sheet  construct  two  complete  turns  of  a  right 
hand  helix  whose  diameter  is  3"  and  pitch  2"  (Arts.  70  and  71).  Sometimes  in 
drawing  a  helix  a  templet  is  made  by  laying  out  the  curve  on  a  piece  of  cardboard 
or  thin  wood  and  cutting  out  with  a  sharp  knife.  In  the  right  half  of  the  sheet 
draw  as  in  the  layout  Fig.  415,  the  forms  of  the  U.  S.  Std.  thread,  Whitworth  thread 
and  knuckle  thread,  1"  pitch  (Art.  70,  Fig.  139).  Letter  the  name  of  each  form 
under  the  drawing  of  it. 


HELIX  AND  THREAD  FORMS  •     DRAWN  BY 

(Date) I9_    APPROVED  BV 


FIG.  415.— Prob.  161. 


202 


MECHANICAL  DRAWING 


iE     OF   SCHOOL 
LOCATION 


THREAD    REPRESENTATIONS 
Full  Size  (DdteJ_ 


DRAWN  BY 

•)_    APPROVED  BY- 


FIG.  416.— Prob.  163. 


NAME     OF    SCHOOL 


U.S.  STANDARD  BOLTS 


(Dafej I9_ 


APPROVED  BY_ 


FIG.  417.— Prob.  164. 


PROBLEMS 


203 


Draw  nut  here. 


E'   OF  SCHOOL 
LOCATION/ 


T/ASTENIN6S 


(Dcte;_ 


DRAWN  BY 

_  I9_     APPROVED  BY  . 


FIG.  418.— Prob.  165. 


Prob.  163,  Fig.  416.— Locate  center  lines  as  shown  and  draw  the  conventional 
thread  representations  given  in  the  layout  (Art.  71).  These  and  several  other 
conventional  forms  are  in  use  for  representing  screw  threads,  and  are  drawn  here 
for  practice.  On  working  drawings  one  of  the  forms  should  be  selected  and  used 
for  all  thread  representations.  The  casting  drawn  on  the  right  half  of  the  sheet 
has  threaded  holes  represented  conventionally  under  three  different  conditions 
(Art.  71). 

Prob.  164,  Fig.  417. — Locate  the  center  lines.  On  the  upper  line  draw  a  hex 
head  bolt  and  nut  in  the  two  positions  shown,  across  corners  and  across  flats. 

On  the  lower  line  draw  a  square  head  bolt  and  nut  across  corners  and  across 
flats  (Arts.  73,  74,  75). 

Prob.  165,  Fig.  418. — Divide  the  working  space  into  four  spaces  as  shown.  In 
the  upper  left  hand  space  draw  a  stud  and  U.  S.  Standard  nut.  Diameter,  %"; 
length  5";  length  of  thread  on  each  end  IK"-  In  the  upper  right  hand  space  draw 
an  S.  A.  E.  St'd.  bolt  and  nut.  Diameter  %";  length  4"  (Art.  76,  Table  II). 

In  the  lower  left  hand  space  draw  three  forms  of  cap  screws,  at  A,  B,  and  C. 
Diameter  %6";  length  !>£"  (Art.  76,  Table  III). 

In  the  lower  right  hand  space  draw  three  set  screws,  regular  head,  low  head, 
and  headless.  Diameter  %";  length  1^"  (Art.  76,  Fig.  155). 


204 


MECHANICAL  DRAWING 


FIG  419.— Prob/166. 


Prob.  166,  Fig.  419.— Make 
a  complete  working  drawing  of 
one  of  the  plate  couplings  in 
section.  Show  bolts  and  key 
in  position.  Choose  scale.  Di- 
mensions given  in  Table  are 
inches. 

For  \Y±  shaft  use  three  W 

bolts  and  %6"  square  key. 

For  \Y2  shaft  use  three  Y^" 

bolts  and  %"  square  key. 

For  3%  shaft  use  six  %" 

bolts  and  %"  square  key. 

For   4   shaft  use  six   J-8" 

bolts  and  1"  square  key. 

Missing  dimensions  are  to 

be  supplied  by  the  student. 

Prob.  167,  Fig.  420.— Make 
a  three  view  working  drawing 
of  the  bracket  bearing,  com- 
pletely dimensioned.  Draw 
full  size.  Locate  the  views  as 
described  for  Figs.  315  and  316. 


/  Diam 


FIG.  420.— Prob.  167. 


PROBLEMS 


205 


NAME     OF   SCHOOL  CARRIER    IRON 

.OCATION  I   Scale  6*-«' 


APPROVED  BY 


Fio.  421.—  Prob.  168. 


Prob.  168,  Fig.  421.  —  Make  a  three  view  working  drawing  of  the  carrier  iron. 
Scale  6"  =  1'.  Draw  the  front  view  as  a  section.  Draw  a  bottom  view  instead 
of  the  top  view. 


Design  fo  suit 


Base  i  stock 

AH  other  stock 


FIG.  422.— Prob.  169. 


Prob.  169,  Fig.  422. — Make  an  assembly  working  drawing  with  complete 
dimensions,  for  the  book  rack.    Select  views  and  scale. 


206 


MECHANICAL  DRAWING 


,X?//  ho/es  cored  g  d. 


T 


NAME     OF    SCHOOL  RIBBED     CAP 

UOCATION  Scale  6"=  l'  (Date; 


DRAWN  BY" 
APPROVED  BY_ 


FIG.  423.— Prob.  170. 

Prob.  170,  Fig.  423. — Make  a  three  view  working  drawing  with  complete 
dimensions  for  the  ribbed  cap.     Show  the  front  and  side  views  as  half  sections. 


Fio.  424.— Prob.  171. 


Prob.  171,  Fig.  424.-— Make  a  two  view  working  drawing  of  the  plug  wrench. 
Completely  dimension. 


PROBLEMS 


207 


FIG.  425.— Prob.  172. 


Prob.  172,  Fig.  425. — Make  a  three  view  working  drawing  of  the  slide  valve. 
Show  the  front  view  as  a  section.     Completely  dimension. 

Prob.  173,  Fig.  426. — Make  a  two  view  working  drawing  of  the  lever  with  all 
necessary  dimensions. 


FIG.  426.— Prob.  173. 


208 


MECHANICAL  DRAWING 


Prob.  174,  Fig.  427.— Make 
an  assembly  working  drawing 
with  extra  part  views  if  neces- 
sary, from  which  the  costumer 
might  be  built.  Choose  a 
proper  scale. 


Prob.  175,  Fig.  428.— Make 
a  three  view  working  drawing 
of  the  rod  bracket.  Show 
either  the  front  or  side  view  as 
a  half  section. 


Prob.  176,  Fig.  429.— Make 
a  three  view  working  drawing 
of  the  oil  level  gauge  bracket. 
Show  the  part  of  the  front  view 
to  the  left  of  the  irregular  line 
A- A  as  a  section.  A  134"  pipe 
tap  has  an  outside  diameter  of 
1.66".  Ask  your  teacher  about 
pipe  and  pipe  threads. 


FIG.  427.— Prob.  174. 


PROBLEMS 


209 


c 


3  Core  tor  j  bo/ts 


NAME     OF    SCHOOL  ROD  BRACKET 

LOCATION  I   Full  Size  (Ddte;_ 


Fia.  428.— Prob.  175. 


SAE 


li  Pipe  Top. 


NAME     OF   SCHOOL  OIL  LEVEL  GAUGE    BRACKET 

LOCXXTION  I  Full  Size  (Date) 19 _  APPROVED  BV_ 


[Fm.  429.— Prob.  176. 


210 


MECHANICAL  DRAWING 


Prob.  177,  Fig.  430. — Make  an  assembly  working  drawing  with  extra  part 
views  if  necessary,  for  the  tea  table.  Some  of  the  dimensions  are  not  given, 
and  are  to  be  obtained  from  the  students'  drawing. 


FIG.  430.— Prob.  177. 

.     Prob.  178,  Fig.  431. — Make  a  two   view  working  drawing  of  the  operating 
wheel.    Show  the  left  view  as  a  section. 

Prob.  179,  Fig.  432. — Make  a  two  view  working  drawing  of  the  valve.  Show 
the  left  view  as  a  section.  Locate  point  A,  and  using  it  as  a  center  draw  an  arc 
with  a  9^Hj"  radius  cutting  the  center  line  at  B.  With  B  as  a  center  and  same 
radius  draw  arc  to  locate  point  C. 


PROBLEMS 


211 


FIG.  431.— Prob.  178. 


FIG.  432.— Prob.  179. 


212 


MECHANICAL  DRAWING 


FIG.  433.— Prob.  180. 

Prob.  180,  Fig.1 433. — Make  an  assembly  working  drawing  with  necessary  part 
views  for  the  book  rack. 

Prob.  181,  Fig.  434. — Make  a  complete  working  drawing  of  the  fan  bracket. 
Draw  top,  front  and  left  side  views.  Do  not  draw  bottom  or  right  side. 


FIG.  434.— Prob.  181. 


PROBLEMS 


213 


LAYOUT  FOR  FLANGE 


FIG.  435.—  Prob.  182. 


Prob.  182,  Fig.  435. — Make  a  two  view  working  drawing  of  the  4%"  X 
steel  crosshead  pin.     Note  the  size  and  kind  of  holes  in  the  flange. 


Drill  for/  c 


FIG.  436.— Prob.  183. 

Prob.  183,  Fig.  436. — Given  the  top,  front,  and  left  side  views  of  the  uncoupling 
rod  bracket.     Make  a  working  drawing  showing  the  top,  front,  and  right  side  views. 


214 


MECHANICAL  DRAWING 


FIG.  437.— Prob.  184. 


Prob.  184,  Fig.  437.^Make  a  three  view  working  drawing  of  the  center  plate. 
One  view  to  be  a  section. 

Prob.  185,  Fig.  438. — From  the  details  make  an  assembly  drawing  showing 
two  views  of  the  tool  post.     Dimension  as  required  by  your  instructor. 

Prob.  186,  Fig.  163. — Make  a  detail  drawing  of  each  part  of  the  belt  tightener. 
If  drawn  full  size,  use  two  sheets. 


PROBLEMS 


215 


—  <__ 


H-^: 


* 


t 


Tool  Post-  3 fee/  forging 


77 


Wedge  -  Steel  forging 


Block-  Cold  rolled  sfeel 


FIG.  438,— Prob.  185. 


216 


MECHANICAL  DRAWNIG 


KITCHEN  I   7-x4 

o'li'.rtlii"  I     a?  n 


DINING 


LIVING  RAT 


7-2"xi2-; 


POR.CH 


L— 1        I 

KlKHErt&  PANTRY 
9y*9-i(*|4'-jo'|    PINING 


Mpi  '         ' 


FIG.  439. 


FIG.  440. 


FIG.  441. 


HALL! 

DINING 


£j 


FIG.  442. 


1 


I 
7-WIDE 


LIVING 


DINING 


FIG.  443. 


PROBLEMS 


217 


FIG.  444. 


Probs.  187  to  192,  Figs.  439  to  444. — Select  one  of  the  suggested  floor  plans 
and  make  architectural  working  drawings  as  required  by  your  instructor. 

1.  Basement  plan. 

2.  1st  floor  plan. 

3.  2nd  floor  plan. 

4.  Front  elevation. 

5.  Right  side  elevation. 

6.  Left  side  elevation. 

7.  Rear  elevation. 

8.  Details. 

(Arts.  94  to  100.) 


INDEX 


Alphabet  of  lines,  64 
Angles,  106 

isometric,  44 
to  bisect,  107 
to  transfer,  107 
Architectural  drawing,  95 

details,  103 

elevations,  103 

plans,  96 

symbols,  104 
Arcs  and  tangents,  109,  110,  111 

length  of,  111 

to  draw,  9 
Arrow  heads,  52 
Assembly  drawings,  86 
Auxiliary  views,  37 

B 

Bill  of  material,  69 

Blueprinting,  82 

Bolts,  74^77 

to  draw,  75,  76 

S.  A.  E.  standard,  78 

various,  80 

Bow  pencil,  9,  10 
spacers,  14 


Cabinet  drawing,  48 
Calipers,  58,  59 
Cams,  93 
Cap  screws,  78 

table  for,  79 
Checking  a  drawing,  61 
Circle,  isometric,  45 

tangent  to,  109 

to  draw,  9 

through  three  points,  109 
Compasses,  9 

use  of,  10 


Cone,  development  of,  120-123 
Conventional  representation,  89 

symbols,  80 

Cornice,  pattern  for,  120 
Cross-hatching,  34,  36,  37 

symbols  for,  80 
Curve,  French  or  irregular,  10 
Curved  surfaces,  representation  of,  28,  29 
Cylinder,  development  of,  117 


Decimals,  use  of,  56 

Detail  drawings,  84 

architectural,  103 

Development,  114 
of  cones,  120-123 
of  cylinders,  117 
of  pint  measure,  130 
of  prisms,  116 
of  pyramids,  120,  121 
of  transition  piece,  123 

Dimensioning,  51 

assembled  parts,  57 
for  standard  bolt,  77 
pictorial  sketches,  60 
rules  for,  54,  55 
theory  of,  53 
with  limits,  56 

Dimensions,  placing,  52 
of  U.  S.  bolts,  74 

Dividers,  use  of,  13 

Dotted  lines,  use  of,  28 

Drafting,  84 

Drawing,  architectural,  95 
cabinet,  48 
isometric,  43 
language  of,  1 
mechanical,  2 
oblique,  47 
perspective,  2,  49 
pictorial,  42 
sheet  metal,  113 

Drawing  arcs,  9 


219 


220 


INDEX 


Drawing  board,  3 
Drawing  pencils,  4 
Drawings,  assembly,  86 

checking,  61 

detail,  84 

shade  line,  87 

working,  84 

E 

Elbow,  four  piece,  119 
two  piece,  118 

Ellipse,  111,  112,  113 
approximate,  113 

Erasing,  68 


Finish  marks,  61 
Freehand  sketches,  30 
isometric,  46 
perspective,  50 
problems  for,  32,  33 


Gears,  91 

Geometrical  constructions,  105 


Half  sections,  36 
isometric,  45 
Helix,  to  draw,  71 
Hexagon,  to  draw,  75,  108 


Inclined  letters,  17,  18 

Inclined  surfaces,  representation  of,  27, 

28 
Inking,  65 

order  of,  68 
Intersections,  125 

cylinders,  127 

cylinders  and  cones,  129 

cylinders  and  prisms,  128 

planes  and  curved  surfaces,  130 

prisms,  126 
Isometric  drawing,  43 

to  make,  46 


Laying  out  the  sheet,  135 
Learning  to  draw,  3 
Lettering,  15 

composition  of,  19 

inclined,  17,  18 

roman,  20 

spacing  for,  19 

titles,  68 

vertical,  16 
Line,  to  bisect,  105 

to  divide  by  trial,  13 

to  divide  geometrically,  105 

to  divide  with  scale,  14 

true  length  of,  120,  121 
Lines,  alphabet  of,  64 

dimension,  51 

faulty,  66 

shade,  87 
Locknuts,  77 

M 

Machine  screws,  78 
Measuring,  11,  57 
Mechanical  drawing,  2 

N 

Needle  point,  adjustment  of,  9 
Notes  and  specifications,  60 


Oblique  drawing,  47 

to  make,  48 
Octagon,  to  draw,  109 
Ogee  curve,  111 
Orthographic  projection,  24 


Paper,  attaching,  3 
Parallel  lines,  to  draw,  8 
Pattern,  for  cornice,  120 

for  four  piece  elbow,  119 
for  pint  measure,  130 
for  two  piece  elbow,  118 
Pattern  drafting,  114 
""Penciling,  order  of,  65 


INDEX 


221 


Pencils,  drawing,  4 

sharpening,  4 
Pens,  lettering,  15 
Perpendicular  lines,  to  draw,  9 
Perspective  drawing,  2,  49 
Pictorial  drawing,  42 
Planes  of  projection,  25 
Plans,  architectural,  96 
Prism,  development  of,  116 
Problems,  134-217 

freehand  sketching,  32,  33 
Projection,  auxiliary,  37 

orthographic,  24 

principles  of,  26,  27 
Protractor,  107 
Pyramid,  development  of,  120,  121 


R 


Revolutions,  39 

chart  for,  41 
Roman  letters,  20 
Ruling  lines,  5 


S 


S.'A.  E.  bolts,  78 
Scales,  11,  12 

choice  of,  88 

to  construct,  105 
Screw  threads,  69-73        , 
Seams  and  lap,  132 
Sections,  34 

isometric,  45 

revolved,  90 

symbols  for,  80 

through  ribs,  89 
Set  screws,  79 
Shade  lines,  87 

Shape  description,  theory  of,  21 
Sheet  metal  drafting,  113 
Single  stroke  lettering,  15 
Size  description,  principles  of,  51 
Sketches,  freehand,  30 


Sketching  and  measuring,  57 
Slope  for  inclined  letters,  17 
Spacing,  13 

guide  line,  19 
Specifications,  60 
Square  elbow,  pattern  for,  118 
Stud  bolt,  77 
Surfaces,  curved,  28,  29 
Symbols,  architectural,  103 

conventional,  80 

wiring,  104 


T  square,  use  of,  4,  5 
Tangents,  109,  110,  111 
Technic,  64 

Theory  of  shape  description,  21 
Threads,  screw,  71-73 
Titles,  68 
Tracing,  65,  67 
Transition  piece,  123 
Triangles,  position  of,  7 

to  construct,  107 

use  of,  6,  7,  8,  9 
True  length  of  line,  120 

U 

U.  S.  standard  bolts,  dimensions  of,  74 
V 

Vertical  letters,  16 
Views,  auxiliary,  37 

choice  of,  88 

describing  objects  by,  21 

positions  of,  23 

sectional,  34 

theory  of  relation  of,  24 

W 

Wood  screws,  79 
Working  drawing,  84 


Bl 


14  DAY  USE 

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